Do not use index if no limit or limit + offset > expected tuples unless enable_seqscan = off

.github/workflows/build.yml

@@ -20,6 +20,8 @@ jobs:
             os: ubuntu-20.04
           - postgres: 12
             os: ubuntu-20.04
+          - postgres: 11
+            os: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: ankane/setup-postgres@v1
@@ -57,10 +59,10 @@ jobs:
       - run: |
           brew install cpanm
           cpanm --notest IPC::Run
-          wget -q https://github.com/postgres/postgres/archive/refs/tags/REL_14_10.tar.gz
+          wget -q https://github.com/postgres/postgres/archive/refs/tags/REL_14_5.tar.gz
-          tar xf REL_14_10.tar.gz
+          tar xf REL_14_5.tar.gz
-      - run: make prove_installcheck PROVE_FLAGS="-I ./postgres-REL_14_10/src/test/perl" PERL5LIB="/Users/runner/perl5/lib/perl5"
+      - run: make prove_installcheck PROVE_FLAGS="-I ./postgres-REL_14_5/src/test/perl" PERL5LIB="/Users/runner/perl5/lib/perl5"
-      - run: make clean && /usr/local/opt/llvm@15/bin/scan-build --status-bugs make PG_CFLAGS="-DUSE_ASSERT_CHECKING"
+      - run: make clean && /usr/local/opt/llvm@15/bin/scan-build --status-bugs make
   windows:
     runs-on: windows-latest
     if: ${{ !startsWith(github.ref_name, 'mac') }}
@@ -81,10 +83,10 @@ jobs:
     if: ${{ !startsWith(github.ref_name, 'mac') && !startsWith(github.ref_name, 'windows') }}
     runs-on: ubuntu-latest
     container:
-      image: debian:12
+      image: debian:11
       options: --platform linux/386
     steps:
-      - run: apt-get update && apt-get install -y build-essential git libipc-run-perl postgresql-15 postgresql-server-dev-15 sudo
+      - run: apt-get update && apt-get install -y build-essential git libipc-run-perl postgresql-13 postgresql-server-dev-13 sudo
       - run: service postgresql start
       - run: |
           git clone https://github.com/${{ github.repository }}.git pgvector

CHANGELOG.md

@@ -1,18 +1,11 @@
-## 0.6.0 (2024-01-29)
+## 0.5.2 (unreleased)
 
-If upgrading with Postgres 12 or Docker, see [these notes](https://github.com/pgvector/pgvector#060).
-
-- Changed storage for vector from `extended` to `external`
-- Added support for parallel index builds for HNSW
-- Added validation for GUC parameters
 - Improved performance of HNSW
+- Added support for on-disk parallel index builds for HNSW
 - Reduced memory usage for HNSW index builds
 - Reduced WAL generation for HNSW index builds
 - Fixed error with logical replication
-- Fixed `invalid memory alloc request size` error with HNSW index builds
+- Fixed `invalid memory alloc request size` error with HNSW index build
-- Moved Docker image to `pgvector` org
-- Added Docker tags for each supported version of Postgres
-- Dropped support for Postgres 11
 
 ## 0.5.1 (2023-10-10)
 
@@ -60,7 +53,7 @@ If upgrading with Postgres 12 or Docker, see [these notes](https://github.com/pg
 
 ## 0.4.0 (2023-01-11)
 
-If upgrading with Postgres < 13, see [this note](https://github.com/pgvector/pgvector/blob/v0.4.0/README.md#040).
+If upgrading with Postgres < 13, see [this note](https://github.com/pgvector/pgvector#040).
 
 - Changed text representation for vector elements to match `real`
 - Changed storage for vector from `plain` to `extended`
@@ -77,7 +70,7 @@ If upgrading with Postgres < 13, see [this note](https://github.com/pgvector/pgv
 
 ## 0.3.1 (2022-11-02)
 
-If upgrading from 0.2.7 or 0.3.0, [recreate](https://github.com/pgvector/pgvector/blob/v0.3.1/README.md#031) all `ivfflat` indexes after upgrading to ensure all data is indexed.
+If upgrading from 0.2.7 or 0.3.0, [recreate](https://github.com/pgvector/pgvector#031) all `ivfflat` indexes after upgrading to ensure all data is indexed.
 
 - Fixed issue with inserts silently corrupting `ivfflat` indexes (introduced in 0.2.7)
 - Fixed segmentation fault with index creation when lists > 6500

Dockerfile

@@ -1,4 +1,4 @@
-ARG PG_MAJOR=16
+ARG PG_MAJOR=15
 FROM postgres:$PG_MAJOR
 ARG PG_MAJOR
 

META.json

@@ -2,7 +2,7 @@
 	"name": "vector",
 	"abstract": "Open-source vector similarity search for Postgres",
 	"description": "Supports L2 distance, inner product, and cosine distance",
-	"version": "0.6.0",
+	"version": "0.5.1",
 	"maintainer": [
 		"Andrew Kane <andrew@ankane.org>"
 	],
@@ -12,7 +12,7 @@
 	"prereqs": {
 		"runtime": {
 			"requires": {
-				"PostgreSQL": "12.0.0"
+				"PostgreSQL": "11.0.0"
 			}
 		}
 	},
@@ -20,7 +20,7 @@
 		"vector": {
 			"file": "sql/vector.sql",
 			"docfile": "README.md",
-			"version": "0.6.0",
+			"version": "0.5.1",
 			"abstract": "Open-source vector similarity search for Postgres"
 		}
 	},

Makefile

@@ -1,5 +1,5 @@
 EXTENSION = vector
-EXTVERSION = 0.6.0
+EXTVERSION = 0.5.1
 
 MODULE_big = vector
 DATA = $(wildcard sql/*--*.sql)
@@ -65,17 +65,13 @@ dist:
 	mkdir -p dist
 	git archive --format zip --prefix=$(EXTENSION)-$(EXTVERSION)/ --output dist/$(EXTENSION)-$(EXTVERSION).zip master
 
-# for Docker
-PG_MAJOR ?= 16
-
 .PHONY: docker
 
 docker:
-	docker build --pull --no-cache --build-arg PG_MAJOR=$(PG_MAJOR) -t pgvector/pgvector:pg$(PG_MAJOR) .
+	docker build --pull --no-cache --platform linux/amd64 -t ankane/pgvector:latest .
-	docker build --build-arg PG_MAJOR=$(PG_MAJOR) -t pgvector/pgvector:$(EXTVERSION)-pg$(PG_MAJOR) .
 
 .PHONY: docker-release
 
 docker-release:
-	docker buildx build --push --pull --no-cache --platform linux/amd64,linux/arm64 --build-arg PG_MAJOR=$(PG_MAJOR) -t pgvector/pgvector:pg$(PG_MAJOR) .
+	docker buildx build --push --pull --no-cache --platform linux/amd64,linux/arm64 -t ankane/pgvector:latest .
-	docker buildx build --push --platform linux/amd64,linux/arm64 --build-arg PG_MAJOR=$(PG_MAJOR) -t pgvector/pgvector:$(EXTVERSION)-pg$(PG_MAJOR) .
+	docker buildx build --push --platform linux/amd64,linux/arm64 -t ankane/pgvector:v$(EXTVERSION) .

Makefile.win

@@ -1,5 +1,5 @@
 EXTENSION = vector
-EXTVERSION = 0.6.0
+EXTVERSION = 0.5.1
 
 OBJS = src\hnsw.obj src\hnswbuild.obj src\hnswinsert.obj src\hnswscan.obj src\hnswutils.obj src\hnswvacuum.obj src\ivfbuild.obj src\ivfflat.obj src\ivfinsert.obj src\ivfkmeans.obj src\ivfscan.obj src\ivfutils.obj src\ivfvacuum.obj src\vector.obj
 HEADERS = src\vector.h

README.md

@@ -14,13 +14,11 @@ Plus [ACID](https://en.wikipedia.org/wiki/ACID) compliance, point-in-time recove
 
 ## Installation
 
-### Linux and Mac
-
 Compile and install the extension (supports Postgres 11+)
 
 ```sh
 cd /tmp
-git clone --branch v0.6.0 https://github.com/pgvector/pgvector.git
+git clone --branch v0.5.1 https://github.com/pgvector/pgvector.git
 cd pgvector
 make
 make install # may need sudo
@@ -30,28 +28,6 @@ See the [installation notes](#installation-notes) if you run into issues
 
 You can also install it with [Docker](#docker), [Homebrew](#homebrew), [PGXN](#pgxn), [APT](#apt), [Yum](#yum), or [conda-forge](#conda-forge), and it comes preinstalled with [Postgres.app](#postgresapp) and many [hosted providers](#hosted-postgres). There are also instructions for [GitHub Actions](https://github.com/pgvector/setup-pgvector).
 
-### Windows
-
-Ensure [C++ support in Visual Studio](https://learn.microsoft.com/en-us/cpp/build/building-on-the-command-line?view=msvc-170#download-and-install-the-tools) is installed, and run:
-
-```cmd
-call "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"
-```
-
-Note: The exact path will vary depending on your Visual Studio version and edition
-
-Then use `nmake` to build:
-
-```cmd
-set "PGROOT=C:\Program Files\PostgreSQL\16"
-git clone --branch v0.6.0 https://github.com/pgvector/pgvector.git
-cd pgvector
-nmake /F Makefile.win
-nmake /F Makefile.win install
-```
-
-You can also install it with [Docker](#docker) or [conda-forge](#conda-forge).
-
 ## Getting Started
 
 Enable the extension (do this once in each database where you want to use it)
@@ -264,14 +240,6 @@ HINT:  Increase maintenance_work_mem to speed up builds.
 
 Note: Do not set `maintenance_work_mem` so high that it exhausts the memory on the server
 
-Starting with 0.6.0, you can also speed up index creation by increasing the number of parallel workers (2 by default)
-
-```sql
-SET max_parallel_maintenance_workers = 7; -- plus leader
-```
-
-For a large number of workers, you may also need to increase `max_parallel_workers` (8 by default)
-
 ### Indexing Progress
 
 Check [indexing progress](https://www.postgresql.org/docs/current/progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING) with Postgres 12+
@@ -647,14 +615,34 @@ Note: Replace `16` with your Postgres server version
 
 If compilation fails and the output includes `warning: no such sysroot directory` on Mac, reinstall Xcode Command Line Tools.
 
+### Windows
+
+Support for Windows is currently experimental. Ensure [C++ support in Visual Studio](https://learn.microsoft.com/en-us/cpp/build/building-on-the-command-line?view=msvc-170#download-and-install-the-tools) is installed, and run:
+
+```cmd
+call "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"
+```
+
+Note: The exact path will vary depending on your Visual Studio version and edition
+
+Then use `nmake` to build:
+
+```cmd
+set "PGROOT=C:\Program Files\PostgreSQL\16"
+git clone --branch v0.5.1 https://github.com/pgvector/pgvector.git
+cd pgvector
+nmake /F Makefile.win
+nmake /F Makefile.win install
+```
+
 ## Additional Installation Methods
 
 ### Docker
 
-Get the [Docker image](https://hub.docker.com/r/pgvector/pgvector) with:
+Get the [Docker image](https://hub.docker.com/r/ankane/pgvector) with:
 
 ```sh
-docker pull pgvector/pgvector:pg16
+docker pull ankane/pgvector
 ```
 
 This adds pgvector to the [Postgres image](https://hub.docker.com/_/postgres) (run it the same way).
@@ -662,9 +650,9 @@ This adds pgvector to the [Postgres image](https://hub.docker.com/_/postgres) (r
 You can also build the image manually:
 
 ```sh
-git clone --branch v0.6.0 https://github.com/pgvector/pgvector.git
+git clone --branch v0.5.1 https://github.com/pgvector/pgvector.git
 cd pgvector
-docker build --build-arg PG_MAJOR=16 -t myuser/pgvector .
+docker build --build-arg PG_MAJOR=15 -t myuser/pgvector .
 ```
 
 ### Homebrew
@@ -741,32 +729,28 @@ SELECT extversion FROM pg_extension WHERE extname = 'vector';
 
 ## Upgrade Notes
 
-### 0.6.0
+### 0.4.0
 
-#### Postgres 12
+If upgrading with Postgres < 13, remove this line from `sql/vector--0.3.2--0.4.0.sql`:
-
-If upgrading with Postgres 12, remove this line from `sql/vector--0.5.1--0.6.0.sql`:
 
 ```sql
-ALTER TYPE vector SET (STORAGE = external);
+ALTER TYPE vector SET (STORAGE = extended);
 ```
 
 Then run `make install` and `ALTER EXTENSION vector UPDATE;`.
 
-#### Docker
+### 0.3.1
 
-The Docker image is now published in the `pgvector` org, and there are tags for each supported version of Postgres (rather than a `latest` tag).
+If upgrading from 0.2.7 or 0.3.0, recreate all `ivfflat` indexes after upgrading to ensure all data is indexed.
 
-```sh
+```sql
-docker pull pgvector/pgvector:pg16
+-- Postgres 12+
-# or
+REINDEX INDEX CONCURRENTLY index_name;
-docker pull pgvector/pgvector:0.6.0-pg16
-```
 
-Also, if you’ve increased `maintenance_work_mem`, make sure `--shm-size` is at least that size to avoid an error with parallel HNSW index builds.
+-- Postgres < 12
-
+CREATE INDEX CONCURRENTLY temp_name ON table USING ivfflat (column opclass);
-```sh
+DROP INDEX CONCURRENTLY index_name;
-docker run --shm-size=1g ...
+ALTER INDEX temp_name RENAME TO index_name;
 ```
 
 ## Thanks
@@ -812,8 +796,8 @@ make prove_installcheck  # TAP tests
 To run single tests:
 
 ```sh
-make installcheck REGRESS=functions                            # regression test
+make installcheck REGRESS=functions                    # regression test
-make prove_installcheck PROVE_TESTS=test/t/001_ivfflat_wal.pl  # TAP test
+make prove_installcheck PROVE_TESTS=test/t/001_wal.pl  # TAP test
 ```
 
 To enable benchmarking:

sql/vector--0.5.1--0.6.0.sql

@@ -1,5 +0,0 @@
--- complain if script is sourced in psql, rather than via CREATE EXTENSION
-\echo Use "ALTER EXTENSION vector UPDATE TO '0.6.0'" to load this file. \quit
-
--- remove this single line for Postgres < 13
-ALTER TYPE vector SET (STORAGE = external);

sql/vector.sql

@@ -26,7 +26,7 @@ CREATE TYPE vector (
 	TYPMOD_IN = vector_typmod_in,
 	RECEIVE   = vector_recv,
 	SEND      = vector_send,
-	STORAGE   = external
+	STORAGE   = extended
 );
 
 -- functions

src/hnsw.c

@@ -4,57 +4,25 @@
 #include <math.h>
 
 #include "access/amapi.h"
-#include "access/reloptions.h"
-#include "commands/progress.h"
 #include "commands/vacuum.h"
 #include "hnsw.h"
 #include "utils/guc.h"
 #include "utils/selfuncs.h"
 
-#if PG_VERSION_NUM < 150000
+#if PG_VERSION_NUM >= 120000
-#define MarkGUCPrefixReserved(x) EmitWarningsOnPlaceholders(x)
+#include "commands/progress.h"
 #endif
 
 int			hnsw_ef_search;
-int			hnsw_lock_tranche_id;
+bool		hnsw_enable_parallel_build;
 static relopt_kind hnsw_relopt_kind;
 
-/*
- * Assign a tranche ID for our LWLocks. This only needs to be done by one
- * backend, as the tranche ID is remembered in shared memory.
- *
- * This shared memory area is very small, so we just allocate it from the
- * "slop" that PostgreSQL reserves for small allocations like this. If
- * this grows bigger, we should use a shmem_request_hook and
- * RequestAddinShmemSpace() to pre-reserve space for this.
- */
-static void
-HnswInitLockTranche(void)
-{
-	int		   *tranche_ids;
-	bool		found;
-
-	LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
-	tranche_ids = ShmemInitStruct("hnsw LWLock ids",
-								  sizeof(int) * 1,
-								  &found);
-	if (!found)
-		tranche_ids[0] = LWLockNewTrancheId();
-	hnsw_lock_tranche_id = tranche_ids[0];
-	LWLockRelease(AddinShmemInitLock);
-
-	/* Per-backend registration of the tranche ID */
-	LWLockRegisterTranche(hnsw_lock_tranche_id, "HnswBuild");
-}
-
 /*
  * Initialize index options and variables
  */
 void
 HnswInit(void)
 {
-	HnswInitLockTranche();
-
 	hnsw_relopt_kind = add_reloption_kind();
 	add_int_reloption(hnsw_relopt_kind, "m", "Max number of connections",
 					  HNSW_DEFAULT_M, HNSW_MIN_M, HNSW_MAX_M
@@ -73,12 +41,16 @@ HnswInit(void)
 							"Valid range is 1..1000.", &hnsw_ef_search,
 							HNSW_DEFAULT_EF_SEARCH, HNSW_MIN_EF_SEARCH, HNSW_MAX_EF_SEARCH, PGC_USERSET, 0, NULL, NULL, NULL);
 
-	MarkGUCPrefixReserved("hnsw");
+	/* Behind a variable for now since can be slower than building in memory */
+	DefineCustomBoolVariable("hnsw.enable_parallel_build", "Enables or disables building indexes in parallel",
+							 NULL, &hnsw_enable_parallel_build,
+							 false, PGC_USERSET, 0, NULL, NULL, NULL);
 }
 
 /*
  * Get the name of index build phase
  */
+#if PG_VERSION_NUM >= 120000
 static char *
 hnswbuildphasename(int64 phasenum)
 {
@@ -92,6 +64,7 @@ hnswbuildphasename(int64 phasenum)
 			return NULL;
 	}
 }
+#endif
 
 /*
  * Estimate the cost of an index scan
@@ -106,6 +79,9 @@ hnswcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
 	int			m;
 	int			entryLevel;
 	Relation	index;
+#if PG_VERSION_NUM < 120000
+	List	   *qinfos;
+#endif
 
 	/* Never use index without order */
 	if (path->indexorderbys == NULL)
@@ -118,6 +94,20 @@ hnswcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
 		return;
 	}
 
+	/*
+	 * Do not use index if no limit or limit + offset > ef_search unless
+	 * enable_seqscan = off
+	 */
+	if (root->limit_tuples < 0 || root->limit_tuples > hnsw_ef_search)
+	{
+		*indexStartupCost = 1.0e10 - 1;
+		*indexTotalCost = 1.0e10 - 1;
+		*indexSelectivity = 0;
+		*indexCorrelation = 0;
+		*indexPages = 0;
+		return;
+	}
+
 	MemSet(&costs, 0, sizeof(costs));
 
 	index = index_open(path->indexinfo->indexoid, NoLock);
@@ -131,7 +121,12 @@ hnswcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
 	/* Account for number of tuples (or entry level), m, and ef_search */
 	costs.numIndexTuples = (entryLevel + 2) * m;
 
+#if PG_VERSION_NUM >= 120000
 	genericcostestimate(root, path, loop_count, &costs);
+#else
+	qinfos = deconstruct_indexquals(path);
+	genericcostestimate(root, path, loop_count, qinfos, &costs);
+#endif
 
 	/* Use total cost since most work happens before first tuple is returned */
 	*indexStartupCost = costs.indexTotalCost;
@@ -225,7 +220,9 @@ hnswhandler(PG_FUNCTION_ARGS)
 	amroutine->amcostestimate = hnswcostestimate;
 	amroutine->amoptions = hnswoptions;
 	amroutine->amproperty = NULL;	/* TODO AMPROP_DISTANCE_ORDERABLE */
+#if PG_VERSION_NUM >= 120000
 	amroutine->ambuildphasename = hnswbuildphasename;
+#endif
 	amroutine->amvalidate = hnswvalidate;
 #if PG_VERSION_NUM >= 140000
 	amroutine->amadjustmembers = NULL;

src/hnsw.h

@@ -3,17 +3,21 @@
 
 #include "postgres.h"
 
-#include "access/genam.h"
+#include "access/generic_xlog.h"
 #include "access/parallel.h"
-#include "lib/pairingheap.h"
+#include "access/reloptions.h"
+#include "lib/ilist.h"
 #include "nodes/execnodes.h"
 #include "port.h"				/* for random() */
-#include "utils/relptr.h"
 #include "utils/sampling.h"
 #include "vector.h"
 
+#if PG_VERSION_NUM < 110000
+#error "Requires PostgreSQL 11+"
+#endif
+
 #if PG_VERSION_NUM < 120000
-#error "Requires PostgreSQL 12+"
+#include "access/relscan.h"
 #endif
 
 #define HNSW_MAX_DIM 2000
@@ -60,13 +64,10 @@
 #define PROGRESS_HNSW_PHASE_LOAD		2
 
 #define HNSW_MAX_SIZE (BLCKSZ - MAXALIGN(SizeOfPageHeaderData) - MAXALIGN(sizeof(HnswPageOpaqueData)) - sizeof(ItemIdData))
-#define HNSW_TUPLE_ALLOC_SIZE BLCKSZ
 
 #define HNSW_ELEMENT_TUPLE_SIZE(size)	MAXALIGN(offsetof(HnswElementTupleData, data) + (size))
 #define HNSW_NEIGHBOR_TUPLE_SIZE(level, m)	MAXALIGN(offsetof(HnswNeighborTupleData, indextids) + ((level) + 2) * (m) * sizeof(ItemPointerData))
 
-#define HNSW_NEIGHBOR_ARRAY_SIZE(lm)	(offsetof(HnswNeighborArray, items) + sizeof(HnswCandidate) * (lm))
-
 #define HnswPageGetOpaque(page)	((HnswPageOpaque) PageGetSpecialPointer(page))
 #define HnswPageGetMeta(page)	((HnswMetaPageData *) PageGetContents(page))
 
@@ -95,62 +96,33 @@
 /* Ensure fits on page and in uint8 */
 #define HnswGetMaxLevel(m) Min(((BLCKSZ - MAXALIGN(SizeOfPageHeaderData) - MAXALIGN(sizeof(HnswPageOpaqueData)) - offsetof(HnswNeighborTupleData, indextids) - sizeof(ItemIdData)) / (sizeof(ItemPointerData)) / (m)) - 2, 255)
 
-#define HnswGetValue(base, element) PointerGetDatum(HnswPtrAccess(base, (element)->value))
+#define HnswGetNeighbors(element, lc) (AssertMacro((element)->level >= (lc)), &(element)->neighbors[lc])
-
-#if PG_VERSION_NUM < 140005
-#define relptr_offset(rp) ((rp).relptr_off - 1)
-#endif
-
-/* Pointer macros */
-#define HnswPtrAccess(base, hp) ((base) == NULL ? (hp).ptr : relptr_access(base, (hp).relptr))
-#define HnswPtrStore(base, hp, value) ((base) == NULL ? (void) ((hp).ptr = (value)) : (void) relptr_store(base, (hp).relptr, value))
-#define HnswPtrIsNull(base, hp) ((base) == NULL ? (hp).ptr == NULL : relptr_is_null((hp).relptr))
-#define HnswPtrEqual(base, hp1, hp2) ((base) == NULL ? (hp1).ptr == (hp2).ptr : relptr_offset((hp1).relptr) == relptr_offset((hp2).relptr))
-
-/* For code paths dedicated to each type */
-#define HnswPtrPointer(hp) (hp).ptr
-#define HnswPtrOffset(hp) relptr_offset((hp).relptr)
 
 /* Variables */
 extern int	hnsw_ef_search;
-extern int	hnsw_lock_tranche_id;
+extern bool hnsw_enable_parallel_build;
-
-typedef struct HnswElementData HnswElementData;
-typedef struct HnswNeighborArray HnswNeighborArray;
-
-#define HnswPtrDeclare(type, relptrtype, ptrtype) \
-	relptr_declare(type, relptrtype); \
-	typedef union { type *ptr; relptrtype relptr; } ptrtype;
-
-/* Pointers that can be absolute or relative */
-/* Use char for DatumPtr so works with Pointer */
-HnswPtrDeclare(HnswElementData, HnswElementRelptr, HnswElementPtr);
-HnswPtrDeclare(HnswNeighborArray, HnswNeighborArrayRelptr, HnswNeighborArrayPtr);
-HnswPtrDeclare(HnswNeighborArrayPtr, HnswNeighborsRelptr, HnswNeighborsPtr);
-HnswPtrDeclare(char, DatumRelptr, DatumPtr);
 
 typedef struct HnswElementData
 {
-	HnswElementPtr next;
+	slist_node	next;
 	ItemPointerData heaptids[HNSW_HEAPTIDS];
 	uint8		heaptidsLength;
 	uint8		level;
 	uint8		deleted;
 	uint32		hash;
-	HnswNeighborsPtr neighbors;
+	struct HnswNeighborArray *neighbors;
 	BlockNumber blkno;
 	OffsetNumber offno;
 	OffsetNumber neighborOffno;
 	BlockNumber neighborPage;
-	DatumPtr	value;
+	Datum		value;
-	LWLock		lock;
 }			HnswElementData;
 
 typedef HnswElementData * HnswElement;
 
 typedef struct HnswCandidate
 {
-	HnswElementPtr element;
+	HnswElement element;
 	float		distance;
 	bool		closer;
 }			HnswCandidate;
@@ -159,7 +131,7 @@ typedef struct HnswNeighborArray
 {
 	int			length;
 	bool		closerSet;
-	HnswCandidate items[FLEXIBLE_ARRAY_MEMBER];
+	HnswCandidate *items;
 }			HnswNeighborArray;
 
 typedef struct HnswPairingHeapNode
@@ -178,31 +150,27 @@ typedef struct HnswOptions
 
 typedef struct HnswGraph
 {
-	/* Graph state */
+	slist_head	elements;
-	slock_t		lock;
+	HnswElement entryPoint;
-	HnswElementPtr head;
-	double		indtuples;
-
-	/* Entry state */
-	LWLock		entryLock;
-	HnswElementPtr entryPoint;
-
-	/* Allocations state */
-	LWLock		allocatorLock;
 	long		memoryUsed;
 	long		memoryTotal;
-
-	/* Flushed state */
-	LWLock		flushLock;
 	bool		flushed;
+	double		indtuples;
 }			HnswGraph;
 
+typedef struct HnswSpool
+{
+	Relation	heap;
+	Relation	index;
+}			HnswSpool;
+
 typedef struct HnswShared
 {
 	/* Immutable state */
 	Oid			heaprelid;
 	Oid			indexrelid;
 	bool		isconcurrent;
+	int			scantuplesortstates;
 
 	/* Worker progress */
 	ConditionVariable workersdonecv;
@@ -214,10 +182,16 @@ typedef struct HnswShared
 	int			nparticipantsdone;
 	double		reltuples;
 	HnswGraph	graphData;
+
+#if PG_VERSION_NUM < 120000
+	ParallelHeapScanDescData heapdesc;	/* must come last */
+#endif
 }			HnswShared;
 
+#if PG_VERSION_NUM >= 120000
 #define ParallelTableScanFromHnswShared(shared) \
 	(ParallelTableScanDesc) ((char *) (shared) + BUFFERALIGN(sizeof(HnswShared)))
+#endif
 
 typedef struct HnswLeader
 {
@@ -225,15 +199,8 @@ typedef struct HnswLeader
 	int			nparticipanttuplesorts;
 	HnswShared *hnswshared;
 	Snapshot	snapshot;
-	char	   *hnswarea;
 }			HnswLeader;
 
-typedef struct HnswAllocator
-{
-	void	   *(*alloc) (Size size, void *state);
-	void	   *state;
-}			HnswAllocator;
-
 typedef struct HnswBuildState
 {
 	/* Info */
@@ -266,12 +233,10 @@ typedef struct HnswBuildState
 	/* Memory */
 	MemoryContext graphCtx;
 	MemoryContext tmpCtx;
-	HnswAllocator allocator;
 
 	/* Parallel builds */
 	HnswLeader *hnswleader;
 	HnswShared *hnswshared;
-	char	   *hnswarea;
 }			HnswBuildState;
 
 typedef struct HnswMetaPageData
@@ -370,24 +335,23 @@ bool		HnswNormValue(FmgrInfo *procinfo, Oid collation, Datum *value, Vector * re
 Buffer		HnswNewBuffer(Relation index, ForkNumber forkNum);
 void		HnswInitPage(Buffer buf, Page page);
 void		HnswInit(void);
-List	   *HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, FmgrInfo *procinfo, Oid collation, int m, bool inserting, HnswElement skipElement);
+List	   *HnswSearchLayer(Datum q, List *ep, int ef, int lc, Relation index, FmgrInfo *procinfo, Oid collation, int m, bool inserting, HnswElement skipElement);
 HnswElement HnswGetEntryPoint(Relation index);
 void		HnswGetMetaPageInfo(Relation index, int *m, HnswElement * entryPoint);
-void	   *HnswAlloc(HnswAllocator * allocator, Size size);
+HnswElement HnswInitElement(ItemPointer tid, int m, double ml, int maxLevel);
-HnswElement HnswInitElement(char *base, ItemPointer tid, int m, double ml, int maxLevel, HnswAllocator * alloc);
 HnswElement HnswInitElementFromBlock(BlockNumber blkno, OffsetNumber offno);
-void		HnswFindElementNeighbors(char *base, HnswElement element, HnswElement entryPoint, Relation index, FmgrInfo *procinfo, Oid collation, int m, int efConstruction, bool existing);
+void		HnswInsertElement(HnswElement element, HnswElement entryPoint, Relation index, FmgrInfo *procinfo, Oid collation, int m, int efConstruction, bool existing);
-HnswCandidate *HnswEntryCandidate(char *base, HnswElement em, Datum q, Relation rel, FmgrInfo *procinfo, Oid collation, bool loadVec);
+HnswCandidate *HnswEntryCandidate(HnswElement em, Datum q, Relation rel, FmgrInfo *procinfo, Oid collation, bool loadVec);
 void		HnswUpdateMetaPage(Relation index, int updateEntry, HnswElement entryPoint, BlockNumber insertPage, ForkNumber forkNum, bool building);
-void		HnswSetNeighborTuple(char *base, HnswNeighborTuple ntup, HnswElement e, int m);
+void		HnswSetNeighborTuple(HnswNeighborTuple ntup, HnswElement e, int m);
 void		HnswAddHeapTid(HnswElement element, ItemPointer heaptid);
-void		HnswInitNeighbors(char *base, HnswElement element, int m, HnswAllocator * alloc);
+void		HnswInitNeighbors(HnswElement element, int m);
-bool		HnswInsertTupleOnDisk(Relation index, Datum value, Datum *values, bool *isnull, ItemPointer heap_tid, bool building);
+bool		HnswInsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heap_tid, Relation heapRel, bool building);
-void		HnswUpdateNeighborsOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement e, int m, bool checkExisting, bool building);
+void		HnswUpdateNeighborPages(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement e, int m, bool checkExisting, bool building);
 void		HnswLoadElementFromTuple(HnswElement element, HnswElementTuple etup, bool loadHeaptids, bool loadVec);
 void		HnswLoadElement(HnswElement element, float *distance, Datum *q, Relation index, FmgrInfo *procinfo, Oid collation, bool loadVec);
-void		HnswSetElementTuple(char *base, HnswElementTuple etup, HnswElement element);
+void		HnswSetElementTuple(HnswElementTuple etup, HnswElement element);
-void		HnswUpdateConnection(char *base, HnswElement element, HnswCandidate * hc, int lm, int lc, int *updateIdx, Relation index, FmgrInfo *procinfo, Oid collation);
+void		HnswUpdateConnection(HnswElement element, HnswCandidate * hc, int m, int lc, int *updateIdx, Relation index, FmgrInfo *procinfo, Oid collation);
 void		HnswLoadNeighbors(HnswElement element, Relation index, int m);
 PGDLLEXPORT void HnswParallelBuildMain(dsm_segment *seg, shm_toc *toc);
 
@@ -407,16 +371,6 @@ void		hnswrescan(IndexScanDesc scan, ScanKey keys, int nkeys, ScanKey orderbys,
 bool		hnswgettuple(IndexScanDesc scan, ScanDirection dir);
 void		hnswendscan(IndexScanDesc scan);
 
-static inline HnswNeighborArray *
-HnswGetNeighbors(char *base, HnswElement element, int lc)
-{
-	HnswNeighborArrayPtr *neighborList = HnswPtrAccess(base, element->neighbors);
-
-	Assert(element->level >= lc);
-
-	return HnswPtrAccess(base, neighborList[lc]);
-}
-
 /* Hash tables */
 typedef struct TidHashEntry
 {
@@ -444,17 +398,4 @@ typedef struct PointerHashEntry
 #define SH_DECLARE
 #include "lib/simplehash.h"
 
-typedef struct OffsetHashEntry
-{
-	Size		offset;
-	char		status;
-}			OffsetHashEntry;
-
-#define SH_PREFIX offsethash
-#define SH_ELEMENT_TYPE OffsetHashEntry
-#define SH_KEY_TYPE Size
-#define SH_SCOPE extern
-#define SH_DECLARE
-#include "lib/simplehash.h"
-
 #endif

src/hnswbuild.c

@@ -1,53 +1,14 @@
-/*
- * The HNSW build happens in two phases:
- *
- * 1. In-memory phase
- *
- * In this first phase, the graph is held completely in memory. When the graph
- * is fully built, or we run out of memory reserved for the build (determined
- * by maintenance_work_mem), we materialize the graph to disk (see
- * FlushPages()), and switch to the on-disk phase.
- *
- * In a parallel build, a large contiguous chunk of shared memory is allocated
- * to hold the graph. Each worker process has its own HnswBuildState struct in
- * private memory, which contains information that doesn't change throughout
- * the build, and pointers to the shared structs in shared memory. The shared
- * memory area is mapped to a different address in each worker process, and
- * 'HnswBuildState.hnswarea' points to the beginning of the shared area in the
- * worker process's address space. All pointers used in the graph are
- * "relative pointers", stored as an offset from 'hnswarea'.
- *
- * Each element is protected by an LWLock. It must be held when reading or
- * modifying the element's neighbors or 'heaptids'.
- *
- * In a non-parallel build, the graph is held in backend-private memory. All
- * the elements are allocated in a dedicated memory context, 'graphCtx', and
- * the pointers used in the graph are regular pointers.
- *
- * 2. On-disk phase
- *
- * In the on-disk phase, the index is built by inserting each vector to the
- * index one by one, just like on INSERT. The only difference is that we don't
- * WAL-log the individual inserts. If the graph fit completely in memory and
- * was fully built in the in-memory phase, the on-disk phase is skipped.
- *
- * After we have finished building the graph, we perform one more scan through
- * the index and write all the pages to the WAL.
- */
 #include "postgres.h"
 
 #include <math.h>
 
 #include "access/parallel.h"
-#include "access/table.h"
-#include "access/tableam.h"
 #include "access/xact.h"
-#include "access/xloginsert.h"
 #include "catalog/index.h"
-#include "commands/progress.h"
 #include "hnsw.h"
 #include "miscadmin.h"
-#include "optimizer/optimizer.h"
+#include "lib/pairingheap.h"
+#include "nodes/pg_list.h"
 #include "storage/bufmgr.h"
 #include "tcop/tcopprot.h"
 #include "utils/datum.h"
@@ -55,24 +16,45 @@
 
 #if PG_VERSION_NUM >= 140000
 #include "utils/backend_progress.h"
-#else
+#elif PG_VERSION_NUM >= 120000
 #include "pgstat.h"
 #endif
 
+#if PG_VERSION_NUM >= 120000
+#include "access/tableam.h"
+#include "commands/progress.h"
+#else
+#define PROGRESS_CREATEIDX_TUPLES_DONE 0
+#endif
+
 #if PG_VERSION_NUM >= 130000
 #define CALLBACK_ITEM_POINTER ItemPointer tid
 #else
 #define CALLBACK_ITEM_POINTER HeapTuple hup
 #endif
 
+#if PG_VERSION_NUM >= 120000
+#define UpdateProgress(index, val) pgstat_progress_update_param(index, val)
+#else
+#define UpdateProgress(index, val) ((void)val)
+#endif
+
 #if PG_VERSION_NUM >= 140000
 #include "utils/backend_status.h"
 #include "utils/wait_event.h"
 #endif
 
+#if PG_VERSION_NUM >= 120000
+#include "access/table.h"
+#include "optimizer/optimizer.h"
+#else
+#include "access/heapam.h"
+#include "optimizer/planner.h"
+#include "pgstat.h"
+#endif
+
 #define PARALLEL_KEY_HNSW_SHARED		UINT64CONST(0xA000000000000001)
-#define PARALLEL_KEY_HNSW_AREA			UINT64CONST(0xA000000000000002)
+#define PARALLEL_KEY_QUERY_TEXT			UINT64CONST(0xA000000000000002)
-#define PARALLEL_KEY_QUERY_TEXT			UINT64CONST(0xA000000000000003)
 
 #if PG_VERSION_NUM < 130000
 #define GENERATIONCHUNK_RAWSIZE (SIZEOF_SIZE_T + SIZEOF_VOID_P * 2)
@@ -141,59 +123,55 @@ HnswBuildAppendPage(Relation index, Buffer *buf, Page *page, ForkNumber forkNum)
 }
 
 /*
- * Create graph pages
+ * Create element pages
  */
 static void
-CreateGraphPages(HnswBuildState * buildstate)
+CreateElementPages(HnswBuildState * buildstate)
 {
 	Relation	index = buildstate->index;
 	ForkNumber	forkNum = buildstate->forkNum;
+	Size		etupAllocSize;
 	Size		maxSize;
 	HnswElementTuple etup;
 	HnswNeighborTuple ntup;
 	BlockNumber insertPage;
-	HnswElement entryPoint;
 	Buffer		buf;
 	Page		page;
-	HnswElementPtr iter = buildstate->graph->head;
+	slist_iter	iter;
-	char	   *base = buildstate->hnswarea;
 
 	/* Calculate sizes */
+	etupAllocSize = BLCKSZ;
 	maxSize = HNSW_MAX_SIZE;
 
 	/* Allocate once */
-	etup = palloc0(HNSW_TUPLE_ALLOC_SIZE);
+	etup = palloc0(etupAllocSize);
-	ntup = palloc0(HNSW_TUPLE_ALLOC_SIZE);
+	ntup = palloc0(BLCKSZ);
 
 	/* Prepare first page */
 	buf = HnswNewBuffer(index, forkNum);
 	page = BufferGetPage(buf);
 	HnswInitPage(buf, page);
 
-	while (!HnswPtrIsNull(base, iter))
+	slist_foreach(iter, &buildstate->graph->elements)
 	{
-		HnswElement element = HnswPtrAccess(base, iter);
+		HnswElement element = slist_container(HnswElementData, next, iter.cur);
 		Size		etupSize;
 		Size		ntupSize;
 		Size		combinedSize;
-		void	   *valuePtr = HnswPtrAccess(base, element->value);
-
-		/* Update iterator */
-		iter = element->next;
 
 		/* Zero memory for each element */
-		MemSet(etup, 0, HNSW_TUPLE_ALLOC_SIZE);
+		MemSet(etup, 0, etupAllocSize);
 
 		/* Calculate sizes */
-		etupSize = HNSW_ELEMENT_TUPLE_SIZE(VARSIZE_ANY(valuePtr));
+		etupSize = HNSW_ELEMENT_TUPLE_SIZE(VARSIZE_ANY(DatumGetPointer(element->value)));
 		ntupSize = HNSW_NEIGHBOR_TUPLE_SIZE(element->level, buildstate->m);
 		combinedSize = etupSize + ntupSize + sizeof(ItemIdData);
 
 		/* Initial size check */
-		if (etupSize > HNSW_TUPLE_ALLOC_SIZE)
+		if (etupSize > etupAllocSize)
 			elog(ERROR, "index tuple too large");
 
-		HnswSetElementTuple(base, etup, element);
+		HnswSetElementTuple(etup, element);
 
 		/* Keep element and neighbors on the same page if possible */
 		if (PageGetFreeSpace(page) < etupSize || (combinedSize <= maxSize && PageGetFreeSpace(page) < combinedSize))
@@ -234,53 +212,45 @@ CreateGraphPages(HnswBuildState * buildstate)
 	MarkBufferDirty(buf);
 	UnlockReleaseBuffer(buf);
 
-	entryPoint = HnswPtrAccess(base, buildstate->graph->entryPoint);
+	HnswUpdateMetaPage(index, HNSW_UPDATE_ENTRY_ALWAYS, buildstate->graph->entryPoint, insertPage, forkNum, true);
-	HnswUpdateMetaPage(index, HNSW_UPDATE_ENTRY_ALWAYS, entryPoint, insertPage, forkNum, true);
 
 	pfree(etup);
 	pfree(ntup);
 }
 
 /*
- * Write neighbor tuples
+ * Create neighbor pages
  */
 static void
-WriteNeighborTuples(HnswBuildState * buildstate)
+CreateNeighborPages(HnswBuildState * buildstate)
 {
 	Relation	index = buildstate->index;
 	ForkNumber	forkNum = buildstate->forkNum;
 	int			m = buildstate->m;
-	HnswElementPtr iter = buildstate->graph->head;
+	slist_iter	iter;
-	char	   *base = buildstate->hnswarea;
 	HnswNeighborTuple ntup;
 
 	/* Allocate once */
-	ntup = palloc0(HNSW_TUPLE_ALLOC_SIZE);
+	ntup = palloc0(BLCKSZ);
 
-	while (!HnswPtrIsNull(base, iter))
+	slist_foreach(iter, &buildstate->graph->elements)
 	{
-		HnswElement element = HnswPtrAccess(base, iter);
+		HnswElement e = slist_container(HnswElementData, next, iter.cur);
 		Buffer		buf;
 		Page		page;
-		Size		ntupSize = HNSW_NEIGHBOR_TUPLE_SIZE(element->level, m);
+		Size		ntupSize = HNSW_NEIGHBOR_TUPLE_SIZE(e->level, m);
-
-		/* Update iterator */
-		iter = element->next;
-
-		/* Zero memory for each element */
-		MemSet(ntup, 0, HNSW_TUPLE_ALLOC_SIZE);
 
 		/* Can take a while, so ensure we can interrupt */
 		/* Needs to be called when no buffer locks are held */
 		CHECK_FOR_INTERRUPTS();
 
-		buf = ReadBufferExtended(index, forkNum, element->neighborPage, RBM_NORMAL, NULL);
+		buf = ReadBufferExtended(index, forkNum, e->neighborPage, RBM_NORMAL, NULL);
 		LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
 		page = BufferGetPage(buf);
 
-		HnswSetNeighborTuple(base, ntup, element, m);
+		HnswSetNeighborTuple(ntup, e, m);
 
-		if (!PageIndexTupleOverwrite(page, element->neighborOffno, (Item) ntup, ntupSize))
+		if (!PageIndexTupleOverwrite(page, e->neighborOffno, (Item) ntup, ntupSize))
 			elog(ERROR, "failed to add index item to \"%s\"", RelationGetRelationName(index));
 
 		/* Commit */
@@ -291,6 +261,24 @@ WriteNeighborTuples(HnswBuildState * buildstate)
 	pfree(ntup);
 }
 
+#ifdef HNSW_MEMORY
+/*
+ * Show memory usage
+ */
+static void
+ShowMemoryUsage(HnswBuildState * buildstate)
+{
+#if PG_VERSION_NUM >= 130000
+	elog(INFO, "graph memory: %zu MB, total memory: %zu MB",
+		 MemoryContextMemAllocated(buildstate->graphCtx, false) / (1024 * 1024),
+		 MemoryContextMemAllocated(CurrentMemoryContext, true) / (1024 * 1024));
+#else
+	MemoryContextStats(CurrentMemoryContext);
+	elog(INFO, "estimated memory: %zu MB", buildstate->memoryUsed / (1024 * 1024));
+#endif
+}
+#endif
+
 /*
  * Flush pages
  */
@@ -298,183 +286,77 @@ static void
 FlushPages(HnswBuildState * buildstate)
 {
 #ifdef HNSW_MEMORY
-	elog(INFO, "memory: %zu MB", buildstate->graph->memoryUsed / (1024 * 1024));
+	ShowMemoryUsage(buildstate);
 #endif
 
 	CreateMetaPage(buildstate);
-	CreateGraphPages(buildstate);
+	CreateElementPages(buildstate);
-	WriteNeighborTuples(buildstate);
+	CreateNeighborPages(buildstate);
 
 	buildstate->graph->flushed = true;
 	MemoryContextReset(buildstate->graphCtx);
 }
 
+#if PG_VERSION_NUM < 130000
 /*
- * Add a heap TID to an existing element
+ * Get the memory used by an element
  */
-static bool
+static long
-AddDuplicateInMemory(HnswElement element, HnswElement dup)
+HnswElementMemory(HnswElement e, int m)
 {
-	LWLockAcquire(&dup->lock, LW_EXCLUSIVE);
+	long		elementSize = sizeof(HnswElementData);
 
-	if (dup->heaptidsLength == HNSW_HEAPTIDS)
+	elementSize += sizeof(HnswNeighborArray) * (e->level + 1);
-	{
+	elementSize += sizeof(HnswCandidate) * (m * (e->level + 2));
-		LWLockRelease(&dup->lock);
+	elementSize += VARSIZE_ANY(DatumGetPointer(e->value));
-		return false;
+	/* Each allocation has a chunk header */
-	}
+	elementSize += (e->level + 4) * GENERATIONCHUNK_RAWSIZE;
-
+	/* Add an extra 5% for alignment and other overhead */
-	HnswAddHeapTid(dup, &element->heaptids[0]);
+	return elementSize * 1.05;
-
-	LWLockRelease(&dup->lock);
-
-	return true;
 }
+#endif
 
 /*
  * Find duplicate element
  */
 static bool
-FindDuplicateInMemory(char *base, HnswElement element)
+HnswFindDuplicateInMemory(HnswElement element)
 {
-	HnswNeighborArray *neighbors = HnswGetNeighbors(base, element, 0);
+	HnswNeighborArray *neighbors = HnswGetNeighbors(element, 0);
-	Datum		value = HnswGetValue(base, element);
 
 	for (int i = 0; i < neighbors->length; i++)
 	{
 		HnswCandidate *neighbor = &neighbors->items[i];
-		HnswElement neighborElement = HnswPtrAccess(base, neighbor->element);
-		Datum		neighborValue = HnswGetValue(base, neighborElement);
 
 		/* Exit early since ordered by distance */
-		if (!datumIsEqual(value, neighborValue, false, -1))
+		if (!datumIsEqual(element->value, neighbor->element->value, false, -1))
 			return false;
 
 		/* Check for space */
-		if (AddDuplicateInMemory(element, neighborElement))
+		if (neighbor->element->heaptidsLength < HNSW_HEAPTIDS)
+		{
+			HnswAddHeapTid(neighbor->element, &element->heaptids[0]);
 			return true;
+		}
 	}
 
 	return false;
 }
 
 /*
- * Add to element list
+ * Insert tuple into in-memory graph
  */
-static void
+static bool
-AddElementInMemory(char *base, HnswGraph * graph, HnswElement element)
+InsertTupleInMemory(Relation index, Datum *values, ItemPointer heaptid, HnswBuildState * buildstate)
-{
-	SpinLockAcquire(&graph->lock);
-	element->next = graph->head;
-	HnswPtrStore(base, graph->head, element);
-	SpinLockRelease(&graph->lock);
-}
-
-/*
- * Update neighbors
- */
-static void
-UpdateNeighborsInMemory(char *base, FmgrInfo *procinfo, Oid collation, HnswElement e, int m)
-{
-	for (int lc = e->level; lc >= 0; lc--)
-	{
-		int			lm = HnswGetLayerM(m, lc);
-		HnswNeighborArray *neighbors = HnswGetNeighbors(base, e, lc);
-
-		for (int i = 0; i < neighbors->length; i++)
-		{
-			HnswCandidate *hc = &neighbors->items[i];
-			HnswElement neighborElement = HnswPtrAccess(base, hc->element);
-
-			/* Keep scan-build happy on Mac x86-64 */
-			Assert(neighborElement);
-
-			/* Use element for lock instead of hc since hc can be replaced */
-			LWLockAcquire(&neighborElement->lock, LW_EXCLUSIVE);
-			HnswUpdateConnection(base, e, hc, lm, lc, NULL, NULL, procinfo, collation);
-			LWLockRelease(&neighborElement->lock);
-		}
-	}
-}
-
-/*
- * Update graph in memory
- */
-static void
-UpdateGraphInMemory(FmgrInfo *procinfo, Oid collation, HnswElement element, int m, int efConstruction, HnswElement entryPoint, HnswBuildState * buildstate)
-{
-	HnswGraph  *graph = buildstate->graph;
-	char	   *base = buildstate->hnswarea;
-
-	/* Look for duplicate */
-	if (FindDuplicateInMemory(base, element))
-		return;
-
-	/* Add element */
-	AddElementInMemory(base, graph, element);
-
-	/* Update neighbors */
-	UpdateNeighborsInMemory(base, procinfo, collation, element, m);
-
-	/* Update entry point if needed (already have lock) */
-	if (entryPoint == NULL || element->level > entryPoint->level)
-		HnswPtrStore(base, graph->entryPoint, element);
-}
-
-/*
- * Insert tuple in memory
- */
-static void
-InsertTupleInMemory(HnswBuildState * buildstate, HnswElement element)
 {
 	FmgrInfo   *procinfo = buildstate->procinfo;
 	Oid			collation = buildstate->collation;
 	HnswGraph  *graph = buildstate->graph;
-	HnswElement entryPoint;
+	HnswElement entryPoint = graph->entryPoint;
-	LWLock	   *entryLock = &graph->entryLock;
 	int			efConstruction = buildstate->efConstruction;
 	int			m = buildstate->m;
-	char	   *base = buildstate->hnswarea;
+	MemoryContext oldCtx;
-
-	/* Get entry point */
-	LWLockAcquire(entryLock, LW_SHARED);
-	entryPoint = HnswPtrAccess(base, graph->entryPoint);
-
-	/* Prevent concurrent inserts when likely updating entry point */
-	if (entryPoint == NULL || element->level > entryPoint->level)
-	{
-		/* Release shared lock */
-		LWLockRelease(entryLock);
-
-		/* Get exclusive lock */
-		LWLockAcquire(entryLock, LW_EXCLUSIVE);
-
-		/* Get latest entry point after lock is acquired */
-		entryPoint = HnswPtrAccess(base, graph->entryPoint);
-	}
-
-	/* Find neighbors for element */
-	HnswFindElementNeighbors(base, element, entryPoint, NULL, procinfo, collation, m, efConstruction, false);
-
-	/* Update graph in memory */
-	UpdateGraphInMemory(procinfo, collation, element, m, efConstruction, entryPoint, buildstate);
-
-	/* Release entry lock */
-	LWLockRelease(entryLock);
-}
-
-/*
- * Insert tuple
- */
-static bool
-InsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heaptid, HnswBuildState * buildstate)
-{
-	HnswGraph  *graph = buildstate->graph;
 	HnswElement element;
-	HnswAllocator *allocator = &buildstate->allocator;
-	Size		valueSize;
-	Pointer		valuePtr;
-	LWLock	   *flushLock = &graph->flushLock;
-	char	   *base = buildstate->hnswarea;
 
 	/* Detoast once for all calls */
 	Datum		value = PointerGetDatum(PG_DETOAST_DATUM(values[0]));
@@ -482,83 +364,73 @@ InsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heaptid, Hn
 	/* Normalize if needed */
 	if (buildstate->normprocinfo != NULL)
 	{
-		if (!HnswNormValue(buildstate->normprocinfo, buildstate->collation, &value, buildstate->normvec))
+		if (!HnswNormValue(buildstate->normprocinfo, collation, &value, buildstate->normvec))
 			return false;
 	}
 
-	/* Get datum size */
+	/* Allocate element in graph memory context */
-	valueSize = VARSIZE_ANY(DatumGetPointer(value));
+	oldCtx = MemoryContextSwitchTo(buildstate->graphCtx);
+	element = HnswInitElement(heaptid, buildstate->m, buildstate->ml, buildstate->maxLevel);
+	element->value = datumCopy(value, false, -1);
+	MemoryContextSwitchTo(oldCtx);
 
-	/* Ensure graph not flushed when inserting */
+	/* Update memory usage */
-	LWLockAcquire(flushLock, LW_SHARED);
+#if PG_VERSION_NUM >= 130000
+	graph->memoryUsed = MemoryContextMemAllocated(buildstate->graphCtx, false);
+#else
+	graph->memoryUsed += HnswElementMemory(element, buildstate->m);
+#endif
 
-	/* Are we in the on-disk phase? */
+	/* Insert element in graph */
-	if (graph->flushed)
+	HnswInsertElement(element, entryPoint, NULL, procinfo, collation, m, efConstruction, false);
+
+	/* Look for duplicate */
+	if (HnswFindDuplicateInMemory(element))
 	{
-		LWLockRelease(flushLock);
+		/* No need to free element since memory unlikely to be reallocated */
-
+		return true;
-		return HnswInsertTupleOnDisk(index, value, values, isnull, heaptid, true);
 	}
 
-	/*
+	/* Add element */
-	 * In a parallel build, the HnswElement is allocated from the shared
+	slist_push_head(&graph->elements, &element->next);
-	 * memory area, so we need to coordinate with other processes.
-	 */
-	LWLockAcquire(&graph->allocatorLock, LW_EXCLUSIVE);
 
-	/*
+	/* Update neighbors */
-	 * Check that we have enough memory available for the new element now that
+	for (int lc = element->level; lc >= 0; lc--)
-	 * we have the allocator lock, and flush pages if needed.
-	 */
-	if (graph->memoryUsed >= graph->memoryTotal)
 	{
-		LWLockRelease(&graph->allocatorLock);
+		int			lm = HnswGetLayerM(m, lc);
+		HnswNeighborArray *neighbors = HnswGetNeighbors(element, lc);
 
-		LWLockRelease(flushLock);
+		for (int i = 0; i < neighbors->length; i++)
-		LWLockAcquire(flushLock, LW_EXCLUSIVE);
+			HnswUpdateConnection(element, &neighbors->items[i], lm, lc, NULL, NULL, procinfo, collation);
-
-		if (!graph->flushed)
-		{
-			ereport(NOTICE,
-					(errmsg("hnsw graph no longer fits into maintenance_work_mem after " INT64_FORMAT " tuples", (int64) graph->indtuples),
-					 errdetail("Building will take significantly more time."),
-					 errhint("Increase maintenance_work_mem to speed up builds.")));
-
-			FlushPages(buildstate);
-		}
-
-		LWLockRelease(flushLock);
-
-		return HnswInsertTupleOnDisk(index, value, values, isnull, heaptid, true);
 	}
 
-	/* Ok, we can proceed to allocate the element */
+	/* Update entry point if needed */
-	element = HnswInitElement(base, heaptid, buildstate->m, buildstate->ml, buildstate->maxLevel, allocator);
+	if (entryPoint == NULL || element->level > entryPoint->level)
-	valuePtr = HnswAlloc(allocator, valueSize);
+		graph->entryPoint = element;
-
-	/*
-	 * We have now allocated the space needed for the element, so we don't
-	 * need the allocator lock anymore. Release it and initialize the rest of
-	 * the element.
-	 */
-	LWLockRelease(&graph->allocatorLock);
-
-	/* Copy the datum */
-	memcpy(valuePtr, DatumGetPointer(value), valueSize);
-	HnswPtrStore(base, element->value, valuePtr);
-
-	/* Create a lock for the element */
-	LWLockInitialize(&element->lock, hnsw_lock_tranche_id);
-
-	/* Insert tuple */
-	InsertTupleInMemory(buildstate, element);
-
-	/* Release flush lock */
-	LWLockRelease(flushLock);
 
 	return true;
 }
 
+/*
+ * Acquire a lock if needed
+ */
+static inline void
+HnswLockAcquire(HnswShared * hnswshared)
+{
+	if (hnswshared)
+		SpinLockAcquire(&hnswshared->mutex);
+}
+
+/*
+ * Release a lock if needed
+ */
+static inline void
+HnswLockRelease(HnswShared * hnswshared)
+{
+	if (hnswshared)
+		SpinLockRelease(&hnswshared->mutex);
+}
+
 /*
  * Callback for table_index_build_scan
  */
@@ -568,7 +440,9 @@ BuildCallback(Relation index, CALLBACK_ITEM_POINTER, Datum *values,
 {
 	HnswBuildState *buildstate = (HnswBuildState *) state;
 	HnswGraph  *graph = buildstate->graph;
+	HnswShared *hnswshared = buildstate->hnswshared;
 	MemoryContext oldCtx;
+	bool		inserted;
 
 #if PG_VERSION_NUM < 130000
 	ItemPointer tid = &hup->t_self;
@@ -578,16 +452,31 @@ BuildCallback(Relation index, CALLBACK_ITEM_POINTER, Datum *values,
 	if (isnull[0])
 		return;
 
-	/* Use memory context */
+	/* Flush pages if needed */
+	if (!graph->flushed && graph->memoryUsed >= graph->memoryTotal)
+	{
+		ereport(NOTICE,
+				(errmsg("hnsw graph no longer fits into maintenance_work_mem after " INT64_FORMAT " tuples", (int64) graph->indtuples),
+				 errdetail("Building will take significantly more time."),
+				 errhint("Increase maintenance_work_mem to speed up builds.")));
+
+		FlushPages(buildstate);
+	}
+
 	oldCtx = MemoryContextSwitchTo(buildstate->tmpCtx);
 
 	/* Insert tuple */
-	if (InsertTuple(index, values, isnull, tid, buildstate))
+	if (graph->flushed)
+		inserted = HnswInsertTuple(index, values, isnull, tid, buildstate->heap, true);
+	else
+		inserted = InsertTupleInMemory(index, values, tid, buildstate);
+
+	/* Update progress */
+	if (inserted)
 	{
-		/* Update progress */
+		HnswLockAcquire(hnswshared);
-		SpinLockAcquire(&graph->lock);
+		UpdateProgress(PROGRESS_CREATEIDX_TUPLES_DONE, ++graph->indtuples);
-		pgstat_progress_update_param(PROGRESS_CREATEIDX_TUPLES_DONE, ++graph->indtuples);
+		HnswLockRelease(hnswshared);
-		SpinLockRelease(&graph->lock);
 	}
 
 	/* Reset memory context */
@@ -599,59 +488,14 @@ BuildCallback(Relation index, CALLBACK_ITEM_POINTER, Datum *values,
  * Initialize the graph
  */
 static void
-InitGraph(HnswGraph * graph, char *base, long memoryTotal)
+InitGraph(HnswGraph * graph)
 {
-	HnswPtrStore(base, graph->head, (HnswElement) NULL);
+	slist_init(&graph->elements);
-	HnswPtrStore(base, graph->entryPoint, (HnswElement) NULL);
+	graph->entryPoint = NULL;
 	graph->memoryUsed = 0;
-	graph->memoryTotal = memoryTotal;
+	graph->memoryTotal = maintenance_work_mem * 1024L;
 	graph->flushed = false;
 	graph->indtuples = 0;
-	SpinLockInit(&graph->lock);
-	LWLockInitialize(&graph->entryLock, hnsw_lock_tranche_id);
-	LWLockInitialize(&graph->allocatorLock, hnsw_lock_tranche_id);
-	LWLockInitialize(&graph->flushLock, hnsw_lock_tranche_id);
-}
-
-/*
- * Initialize an allocator
- */
-static void
-InitAllocator(HnswAllocator * allocator, void *(*alloc) (Size size, void *state), void *state)
-{
-	allocator->alloc = alloc;
-	allocator->state = state;
-}
-
-/*
- * Memory context allocator
- */
-static void *
-HnswMemoryContextAlloc(Size size, void *state)
-{
-	HnswBuildState *buildstate = (HnswBuildState *) state;
-	void	   *chunk = MemoryContextAlloc(buildstate->graphCtx, size);
-
-#if PG_VERSION_NUM >= 130000
-	buildstate->graphData.memoryUsed = MemoryContextMemAllocated(buildstate->graphCtx, false);
-#else
-	buildstate->graphData.memoryUsed += MAXALIGN(size);
-#endif
-
-	return chunk;
-}
-
-/*
- * Shared memory allocator
- */
-static void *
-HnswSharedMemoryAlloc(Size size, void *state)
-{
-	HnswBuildState *buildstate = (HnswBuildState *) state;
-	void	   *chunk = buildstate->hnswarea + buildstate->graph->memoryUsed;
-
-	buildstate->graph->memoryUsed += MAXALIGN(size);
-	return chunk;
 }
 
 /*
@@ -687,7 +531,7 @@ InitBuildState(HnswBuildState * buildstate, Relation heap, Relation index, Index
 	buildstate->normprocinfo = HnswOptionalProcInfo(index, HNSW_NORM_PROC);
 	buildstate->collation = index->rd_indcollation[0];
 
-	InitGraph(&buildstate->graphData, NULL, maintenance_work_mem * 1024L);
+	InitGraph(&buildstate->graphData);
 	buildstate->graph = &buildstate->graphData;
 	buildstate->ml = HnswGetMl(buildstate->m);
 	buildstate->maxLevel = HnswGetMaxLevel(buildstate->m);
@@ -705,11 +549,8 @@ InitBuildState(HnswBuildState * buildstate, Relation heap, Relation index, Index
 											   "Hnsw build temporary context",
 											   ALLOCSET_DEFAULT_SIZES);
 
-	InitAllocator(&buildstate->allocator, &HnswMemoryContextAlloc, buildstate);
-
 	buildstate->hnswleader = NULL;
 	buildstate->hnswshared = NULL;
-	buildstate->hnswarea = NULL;
 }
 
 /*
@@ -740,7 +581,6 @@ ParallelHeapScan(HnswBuildState * buildstate)
 		if (hnswshared->nparticipantsdone == nparticipanttuplesorts)
 		{
 			buildstate->graph = &hnswshared->graphData;
-			buildstate->hnswarea = buildstate->hnswleader->hnswarea;
 			reltuples = hnswshared->reltuples;
 			SpinLockRelease(&hnswshared->mutex);
 			break;
@@ -760,25 +600,35 @@ ParallelHeapScan(HnswBuildState * buildstate)
  * Perform a worker's portion of a parallel insert
  */
 static void
-HnswParallelScanAndInsert(Relation heapRel, Relation indexRel, HnswShared * hnswshared, char *hnswarea, bool progress)
+HnswParallelScanAndInsert(HnswSpool * hnswspool, HnswShared * hnswshared, bool progress)
 {
 	HnswBuildState buildstate;
+#if PG_VERSION_NUM >= 120000
 	TableScanDesc scan;
+#else
+	HeapScanDesc scan;
+#endif
 	double		reltuples;
 	IndexInfo  *indexInfo;
 
 	/* Join parallel scan */
-	indexInfo = BuildIndexInfo(indexRel);
+	indexInfo = BuildIndexInfo(hnswspool->index);
 	indexInfo->ii_Concurrent = hnswshared->isconcurrent;
-	InitBuildState(&buildstate, heapRel, indexRel, indexInfo, MAIN_FORKNUM);
+	InitBuildState(&buildstate, hnswspool->heap, hnswspool->index, indexInfo, MAIN_FORKNUM);
 	buildstate.graph = &hnswshared->graphData;
-	buildstate.hnswarea = hnswarea;
+	buildstate.hnswshared = hnswshared;
-	InitAllocator(&buildstate.allocator, &HnswSharedMemoryAlloc, &buildstate);
+#if PG_VERSION_NUM >= 120000
-	scan = table_beginscan_parallel(heapRel,
+	scan = table_beginscan_parallel(hnswspool->heap,
 									ParallelTableScanFromHnswShared(hnswshared));
-	reltuples = table_index_build_scan(heapRel, indexRel, indexInfo,
+	reltuples = table_index_build_scan(hnswspool->heap, hnswspool->index, indexInfo,
 									   true, progress, BuildCallback,
 									   (void *) &buildstate, scan);
+#else
+	scan = heap_beginscan_parallel(hnswspool->heap, &hnswshared->heapdesc);
+	reltuples = IndexBuildHeapScan(hnswspool->heap, hnswspool->index, indexInfo,
+								   true, BuildCallback,
+								   (void *) &buildstate, scan);
+#endif
 
 	/* Record statistics */
 	SpinLockAcquire(&hnswshared->mutex);
@@ -805,8 +655,8 @@ void
 HnswParallelBuildMain(dsm_segment *seg, shm_toc *toc)
 {
 	char	   *sharedquery;
+	HnswSpool  *hnswspool;
 	HnswShared *hnswshared;
-	char	   *hnswarea;
 	Relation	heapRel;
 	Relation	indexRel;
 	LOCKMODE	heapLockmode;
@@ -835,17 +685,28 @@ HnswParallelBuildMain(dsm_segment *seg, shm_toc *toc)
 	}
 
 	/* Open relations within worker */
+#if PG_VERSION_NUM >= 120000
 	heapRel = table_open(hnswshared->heaprelid, heapLockmode);
+#else
+	heapRel = heap_open(hnswshared->heaprelid, heapLockmode);
+#endif
 	indexRel = index_open(hnswshared->indexrelid, indexLockmode);
 
-	hnswarea = shm_toc_lookup(toc, PARALLEL_KEY_HNSW_AREA, false);
+	/* Initialize worker's own spool */
+	hnswspool = (HnswSpool *) palloc0(sizeof(HnswSpool));
+	hnswspool->heap = heapRel;
+	hnswspool->index = indexRel;
 
 	/* Perform inserts */
-	HnswParallelScanAndInsert(heapRel, indexRel, hnswshared, hnswarea, false);
+	HnswParallelScanAndInsert(hnswspool, hnswshared, false);
 
 	/* Close relations within worker */
 	index_close(indexRel, indexLockmode);
+#if PG_VERSION_NUM >= 120000
 	table_close(heapRel, heapLockmode);
+#else
+	heap_close(heapRel, heapLockmode);
+#endif
 }
 
 /*
@@ -870,7 +731,19 @@ HnswEndParallel(HnswLeader * hnswleader)
 static Size
 ParallelEstimateShared(Relation heap, Snapshot snapshot)
 {
+#if PG_VERSION_NUM >= 120000
 	return add_size(BUFFERALIGN(sizeof(HnswShared)), table_parallelscan_estimate(heap, snapshot));
+#else
+	if (!IsMVCCSnapshot(snapshot))
+	{
+		Assert(snapshot == SnapshotAny);
+		return sizeof(HnswShared);
+	}
+
+	return add_size(offsetof(HnswShared, heapdesc) +
+					offsetof(ParallelHeapScanDescData, phs_snapshot_data),
+					EstimateSnapshotSpace(snapshot));
+#endif
 }
 
 /*
@@ -880,9 +753,15 @@ static void
 HnswLeaderParticipateAsWorker(HnswBuildState * buildstate)
 {
 	HnswLeader *hnswleader = buildstate->hnswleader;
+	HnswSpool  *leaderworker;
+
+	/* Allocate memory and initialize private spool */
+	leaderworker = (HnswSpool *) palloc0(sizeof(HnswSpool));
+	leaderworker->heap = buildstate->heap;
+	leaderworker->index = buildstate->index;
 
 	/* Perform work common to all participants */
-	HnswParallelScanAndInsert(buildstate->heap, buildstate->index, hnswleader->hnswshared, hnswleader->hnswarea, true);
+	HnswParallelScanAndInsert(leaderworker, hnswleader->hnswshared, true);
 }
 
 /*
@@ -892,12 +771,10 @@ static void
 HnswBeginParallel(HnswBuildState * buildstate, bool isconcurrent, int request)
 {
 	ParallelContext *pcxt;
+	int			scantuplesortstates;
 	Snapshot	snapshot;
 	Size		esthnswshared;
-	Size		esthnswarea;
-	Size		estother;
 	HnswShared *hnswshared;
-	char	   *hnswarea;
 	HnswLeader *hnswleader = (HnswLeader *) palloc0(sizeof(HnswLeader));
 	bool		leaderparticipates = true;
 	int			querylen;
@@ -909,7 +786,13 @@ HnswBeginParallel(HnswBuildState * buildstate, bool isconcurrent, int request)
 	/* Enter parallel mode and create context */
 	EnterParallelMode();
 	Assert(request > 0);
+#if PG_VERSION_NUM >= 120000
 	pcxt = CreateParallelContext("vector", "HnswParallelBuildMain", request);
+#else
+	pcxt = CreateParallelContext("vector", "HnswParallelBuildMain", request, true);
+#endif
+
+	scantuplesortstates = leaderparticipates ? request + 1 : request;
 
 	/* Get snapshot for table scan */
 	if (!isconcurrent)
@@ -920,17 +803,7 @@ HnswBeginParallel(HnswBuildState * buildstate, bool isconcurrent, int request)
 	/* Estimate size of workspaces */
 	esthnswshared = ParallelEstimateShared(buildstate->heap, snapshot);
 	shm_toc_estimate_chunk(&pcxt->estimator, esthnswshared);
-
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
-	/* Leave space for other objects in shared memory */
-	/* Docker has a default limit of 64 MB for shm_size */
-	/* which happens to be the default value of maintenance_work_mem */
-	esthnswarea = maintenance_work_mem * 1024L;
-	estother = 3 * 1024 * 1024;
-	if (esthnswarea > estother)
-		esthnswarea -= estother;
-
-	shm_toc_estimate_chunk(&pcxt->estimator, esthnswarea);
-	shm_toc_estimate_keys(&pcxt->estimator, 2);
 
 	/* Finally, estimate PARALLEL_KEY_QUERY_TEXT space */
 	if (debug_query_string)
@@ -961,21 +834,25 @@ HnswBeginParallel(HnswBuildState * buildstate, bool isconcurrent, int request)
 	hnswshared->heaprelid = RelationGetRelid(buildstate->heap);
 	hnswshared->indexrelid = RelationGetRelid(buildstate->index);
 	hnswshared->isconcurrent = isconcurrent;
+	hnswshared->scantuplesortstates = scantuplesortstates;
 	ConditionVariableInit(&hnswshared->workersdonecv);
 	SpinLockInit(&hnswshared->mutex);
 	/* Initialize mutable state */
 	hnswshared->nparticipantsdone = 0;
 	hnswshared->reltuples = 0;
+	InitGraph(&hnswshared->graphData);
+	/* TODO Support in-memory builds */
+	hnswshared->graphData.memoryTotal = 0;
+	hnswshared->graphData.flushed = true;
+#if PG_VERSION_NUM >= 120000
 	table_parallelscan_initialize(buildstate->heap,
 								  ParallelTableScanFromHnswShared(hnswshared),
 								  snapshot);
-
+#else
-	hnswarea = (char *) shm_toc_allocate(pcxt->toc, esthnswarea);
+	heap_parallelscan_initialize(&hnswshared->heapdesc, buildstate->heap, snapshot);
-	/* Report less than allocated so never fails */
+#endif
-	InitGraph(&hnswshared->graphData, hnswarea, esthnswarea - 1024 * 1024);
 
 	shm_toc_insert(pcxt->toc, PARALLEL_KEY_HNSW_SHARED, hnswshared);
-	shm_toc_insert(pcxt->toc, PARALLEL_KEY_HNSW_AREA, hnswarea);
 
 	/* Store query string for workers */
 	if (debug_query_string)
@@ -995,7 +872,6 @@ HnswBeginParallel(HnswBuildState * buildstate, bool isconcurrent, int request)
 		hnswleader->nparticipanttuplesorts++;
 	hnswleader->hnswshared = hnswshared;
 	hnswleader->snapshot = snapshot;
-	hnswleader->hnswarea = hnswarea;
 
 	/* If no workers were successfully launched, back out (do serial build) */
 	if (pcxt->nworkers_launched == 0)
@@ -1047,15 +923,19 @@ BuildGraph(HnswBuildState * buildstate, ForkNumber forkNum)
 {
 	int			parallel_workers = 0;
 
-	pgstat_progress_update_param(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_HNSW_PHASE_LOAD);
+	UpdateProgress(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_HNSW_PHASE_LOAD);
 
 	/* Calculate parallel workers */
-	if (buildstate->heap != NULL)
+	if (buildstate->heap != NULL && hnsw_enable_parallel_build)
 		parallel_workers = ComputeParallelWorkers(buildstate->heap, buildstate->index);
 
 	/* Attempt to launch parallel worker scan when required */
 	if (parallel_workers > 0)
+	{
+		/* TODO Support in-memory builds */
+		FlushPages(buildstate);
 		HnswBeginParallel(buildstate, buildstate->indexInfo->ii_Concurrent, parallel_workers);
+	}
 
 	/* Add tuples to graph */
 	if (buildstate->heap != NULL)
@@ -1063,8 +943,15 @@ BuildGraph(HnswBuildState * buildstate, ForkNumber forkNum)
 		if (buildstate->hnswleader)
 			buildstate->reltuples = ParallelHeapScan(buildstate);
 		else
+		{
+#if PG_VERSION_NUM >= 120000
 			buildstate->reltuples = table_index_build_scan(buildstate->heap, buildstate->index, buildstate->indexInfo,
 														   true, true, BuildCallback, (void *) buildstate, NULL);
+#else
+			buildstate->reltuples = IndexBuildHeapScan(buildstate->heap, buildstate->index, buildstate->indexInfo,
+													   true, BuildCallback, (void *) buildstate, NULL);
+#endif
+		}
 
 		buildstate->indtuples = buildstate->graph->indtuples;
 	}
@@ -1078,6 +965,22 @@ BuildGraph(HnswBuildState * buildstate, ForkNumber forkNum)
 		HnswEndParallel(buildstate->hnswleader);
 }
 
+#if PG_VERSION_NUM < 110008
+void
+log_newpage_range(Relation rel, ForkNumber forkNum, BlockNumber startblk, BlockNumber endblk, bool page_std)
+{
+	for (BlockNumber blkno = startblk; blkno < endblk; blkno++)
+	{
+		Buffer		buf = ReadBufferExtended(rel, forkNum, blkno, RBM_NORMAL, NULL);
+
+		LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
+		MarkBufferDirty(buf);
+		log_newpage_buffer(buf, page_std);
+		UnlockReleaseBuffer(buf);
+	}
+}
+#endif
+
 /*
  * Build the index
  */

src/hnswinsert.c

@@ -2,7 +2,6 @@
 
 #include <math.h>
 
-#include "access/generic_xlog.h"
 #include "hnsw.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
@@ -117,7 +116,7 @@ HnswInsertAppendPage(Relation index, Buffer *nbuf, Page *npage, GenericXLogState
  * Add to element and neighbor pages
  */
 static void
-AddElementOnDisk(Relation index, HnswElement e, int m, BlockNumber insertPage, BlockNumber *updatedInsertPage, bool building)
+WriteNewElementPages(Relation index, HnswElement e, int m, BlockNumber insertPage, BlockNumber *updatedInsertPage, bool building)
 {
 	Buffer		buf;
 	Page		page;
@@ -135,10 +134,9 @@ AddElementOnDisk(Relation index, HnswElement e, int m, BlockNumber insertPage, B
 	OffsetNumber freeOffno = InvalidOffsetNumber;
 	OffsetNumber freeNeighborOffno = InvalidOffsetNumber;
 	BlockNumber newInsertPage = InvalidBlockNumber;
-	char	   *base = NULL;
 
 	/* Calculate sizes */
-	etupSize = HNSW_ELEMENT_TUPLE_SIZE(VARSIZE_ANY(HnswPtrAccess(base, e->value)));
+	etupSize = HNSW_ELEMENT_TUPLE_SIZE(VARSIZE_ANY(DatumGetPointer(e->value)));
 	ntupSize = HNSW_NEIGHBOR_TUPLE_SIZE(e->level, m);
 	combinedSize = etupSize + ntupSize + sizeof(ItemIdData);
 	maxSize = HNSW_MAX_SIZE;
@@ -146,11 +144,11 @@ AddElementOnDisk(Relation index, HnswElement e, int m, BlockNumber insertPage, B
 
 	/* Prepare element tuple */
 	etup = palloc0(etupSize);
-	HnswSetElementTuple(base, etup, e);
+	HnswSetElementTuple(etup, e);
 
 	/* Prepare neighbor tuple */
 	ntup = palloc0(ntupSize);
-	HnswSetNeighborTuple(base, ntup, e, m);
+	HnswSetNeighborTuple(ntup, e, m);
 
 	/* Find a page (or two if needed) to insert the tuples */
 	for (;;)
@@ -340,14 +338,12 @@ ConnectionExists(HnswElement e, HnswNeighborTuple ntup, int startIdx, int lm)
  * Update neighbors
  */
 void
-HnswUpdateNeighborsOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement e, int m, bool checkExisting, bool building)
+HnswUpdateNeighborPages(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement e, int m, bool checkExisting, bool building)
 {
-	char	   *base = NULL;
-
 	for (int lc = e->level; lc >= 0; lc--)
 	{
 		int			lm = HnswGetLayerM(m, lc);
-		HnswNeighborArray *neighbors = HnswGetNeighbors(base, e, lc);
+		HnswNeighborArray *neighbors = HnswGetNeighbors(e, lc);
 
 		for (int i = 0; i < neighbors->length; i++)
 		{
@@ -355,15 +351,16 @@ HnswUpdateNeighborsOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, Hns
 			Buffer		buf;
 			Page		page;
 			GenericXLogState *state;
+			ItemId		itemid;
 			HnswNeighborTuple ntup;
+			Size		ntupSize;
 			int			idx = -1;
 			int			startIdx;
-			HnswElement neighborElement = HnswPtrAccess(base, hc->element);
+			OffsetNumber offno = hc->element->neighborOffno;
-			OffsetNumber offno = neighborElement->neighborOffno;
 
 			/* Get latest neighbors since they may have changed */
 			/* Do not lock yet since selecting neighbors can take time */
-			HnswLoadNeighbors(neighborElement, index, m);
+			HnswLoadNeighbors(hc->element, index, m);
 
 			/*
 			 * Could improve performance for vacuuming by checking neighbors
@@ -373,14 +370,14 @@ HnswUpdateNeighborsOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, Hns
 			 */
 
 			/* Select neighbors */
-			HnswUpdateConnection(NULL, e, hc, lm, lc, &idx, index, procinfo, collation);
+			HnswUpdateConnection(e, hc, lm, lc, &idx, index, procinfo, collation);
 
 			/* New element was not selected as a neighbor */
 			if (idx == -1)
 				continue;
 
 			/* Register page */
-			buf = ReadBuffer(index, neighborElement->neighborPage);
+			buf = ReadBuffer(index, hc->element->neighborPage);
 			LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
 			if (building)
 			{
@@ -394,10 +391,12 @@ HnswUpdateNeighborsOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, Hns
 			}
 
 			/* Get tuple */
-			ntup = (HnswNeighborTuple) PageGetItem(page, PageGetItemId(page, offno));
+			itemid = PageGetItemId(page, offno);
+			ntup = (HnswNeighborTuple) PageGetItem(page, itemid);
+			ntupSize = ItemIdGetLength(itemid);
 
 			/* Calculate index for update */
-			startIdx = (neighborElement->level - lc) * m;
+			startIdx = (hc->element->level - lc) * m;
 
 			/* Check for existing connection */
 			if (checkExisting && ConnectionExists(e, ntup, startIdx, lm))
@@ -423,9 +422,13 @@ HnswUpdateNeighborsOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, Hns
 			{
 				ItemPointer indextid = &ntup->indextids[idx];
 
-				/* Update neighbor on the buffer */
+				/* Update neighbor */
 				ItemPointerSet(indextid, e->blkno, e->offno);
 
+				/* Overwrite tuple */
+				if (!PageIndexTupleOverwrite(page, offno, (Item) ntup, ntupSize))
+					elog(ERROR, "failed to add index item to \"%s\"", RelationGetRelationName(index));
+
 				/* Commit */
 				if (building)
 					MarkBufferDirty(buf);
@@ -444,12 +447,14 @@ HnswUpdateNeighborsOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, Hns
  * Add a heap TID to an existing element
  */
 static bool
-AddDuplicateOnDisk(Relation index, HnswElement element, HnswElement dup, bool building)
+HnswAddDuplicate(Relation index, HnswElement element, HnswElement dup, bool building)
 {
 	Buffer		buf;
 	Page		page;
 	GenericXLogState *state;
+	ItemId		itemid;
 	HnswElementTuple etup;
+	Size		etupSize;
 	int			i;
 
 	/* Read page */
@@ -467,7 +472,9 @@ AddDuplicateOnDisk(Relation index, HnswElement element, HnswElement dup, bool bu
 	}
 
 	/* Find space */
-	etup = (HnswElementTuple) PageGetItem(page, PageGetItemId(page, dup->offno));
+	itemid = PageGetItemId(page, dup->offno);
+	etup = (HnswElementTuple) PageGetItem(page, itemid);
+	etupSize = ItemIdGetLength(itemid);
 	for (i = 0; i < HNSW_HEAPTIDS; i++)
 	{
 		if (!ItemPointerIsValid(&etup->heaptids[i]))
@@ -483,9 +490,13 @@ AddDuplicateOnDisk(Relation index, HnswElement element, HnswElement dup, bool bu
 		return false;
 	}
 
-	/* Add heap TID, modifying the tuple on the page directly */
+	/* Add heap TID */
 	etup->heaptids[i] = element->heaptids[0];
 
+	/* Overwrite tuple */
+	if (!PageIndexTupleOverwrite(page, dup->offno, (Item) etup, etupSize))
+		elog(ERROR, "failed to add index item to \"%s\"", RelationGetRelationName(index));
+
 	/* Commit */
 	if (building)
 		MarkBufferDirty(buf);
@@ -500,23 +511,19 @@ AddDuplicateOnDisk(Relation index, HnswElement element, HnswElement dup, bool bu
  * Find duplicate element
  */
 static bool
-FindDuplicateOnDisk(Relation index, HnswElement element, bool building)
+HnswFindDuplicate(Relation index, HnswElement element, bool building)
 {
-	char	   *base = NULL;
+	HnswNeighborArray *neighbors = HnswGetNeighbors(element, 0);
-	HnswNeighborArray *neighbors = HnswGetNeighbors(base, element, 0);
-	Datum		value = HnswGetValue(base, element);
 
 	for (int i = 0; i < neighbors->length; i++)
 	{
 		HnswCandidate *neighbor = &neighbors->items[i];
-		HnswElement neighborElement = HnswPtrAccess(base, neighbor->element);
-		Datum		neighborValue = HnswGetValue(base, neighborElement);
 
 		/* Exit early since ordered by distance */
-		if (!datumIsEqual(value, neighborValue, false, -1))
+		if (!datumIsEqual(element->value, neighbor->element->value, false, -1))
 			return false;
 
-		if (AddDuplicateOnDisk(index, element, neighborElement, building))
+		if (HnswAddDuplicate(index, element, neighbor->element, building))
 			return true;
 	}
 
@@ -524,26 +531,26 @@ FindDuplicateOnDisk(Relation index, HnswElement element, bool building)
 }
 
 /*
- * Update graph on disk
+ * Write changes to disk
  */
 static void
-UpdateGraphOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement element, int m, int efConstruction, HnswElement entryPoint, bool building)
+WriteElement(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement element, int m, int efConstruction, HnswElement entryPoint, bool building)
 {
 	BlockNumber newInsertPage = InvalidBlockNumber;
 
 	/* Look for duplicate */
-	if (FindDuplicateOnDisk(index, element, building))
+	if (HnswFindDuplicate(index, element, building))
 		return;
 
-	/* Add element */
+	/* Write element and neighbor tuples */
-	AddElementOnDisk(index, element, m, GetInsertPage(index), &newInsertPage, building);
+	WriteNewElementPages(index, element, m, GetInsertPage(index), &newInsertPage, building);
 
 	/* Update insert page if needed */
 	if (BlockNumberIsValid(newInsertPage))
 		HnswUpdateMetaPage(index, 0, NULL, newInsertPage, MAIN_FORKNUM, building);
 
 	/* Update neighbors */
-	HnswUpdateNeighborsOnDisk(index, procinfo, collation, element, m, false, building);
+	HnswUpdateNeighborPages(index, procinfo, collation, element, m, false, building);
 
 	/* Update entry point if needed */
 	if (entryPoint == NULL || element->level > entryPoint->level)
@@ -554,8 +561,10 @@ UpdateGraphOnDisk(Relation index, FmgrInfo *procinfo, Oid collation, HnswElement
  * Insert a tuple into the index
  */
 bool
-HnswInsertTupleOnDisk(Relation index, Datum value, Datum *values, bool *isnull, ItemPointer heap_tid, bool building)
+HnswInsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heap_tid, Relation heapRel, bool building)
 {
+	Datum		value;
+	FmgrInfo   *normprocinfo;
 	HnswElement entryPoint;
 	HnswElement element;
 	int			m;
@@ -563,7 +572,17 @@ HnswInsertTupleOnDisk(Relation index, Datum value, Datum *values, bool *isnull,
 	FmgrInfo   *procinfo = index_getprocinfo(index, 1, HNSW_DISTANCE_PROC);
 	Oid			collation = index->rd_indcollation[0];
 	LOCKMODE	lockmode = ShareLock;
-	char	   *base = NULL;
+
+	/* Detoast once for all calls */
+	value = PointerGetDatum(PG_DETOAST_DATUM(values[0]));
+
+	/* Normalize if needed */
+	normprocinfo = HnswOptionalProcInfo(index, HNSW_NORM_PROC);
+	if (normprocinfo != NULL)
+	{
+		if (!HnswNormValue(normprocinfo, collation, &value, NULL))
+			return false;
+	}
 
 	/*
 	 * Get a shared lock. This allows vacuum to ensure no in-flight inserts
@@ -576,8 +595,8 @@ HnswInsertTupleOnDisk(Relation index, Datum value, Datum *values, bool *isnull,
 	HnswGetMetaPageInfo(index, &m, &entryPoint);
 
 	/* Create an element */
-	element = HnswInitElement(base, heap_tid, m, HnswGetMl(m), HnswGetMaxLevel(m), NULL);
+	element = HnswInitElement(heap_tid, m, HnswGetMl(m), HnswGetMaxLevel(m));
-	HnswPtrStore(base, element->value, DatumGetPointer(value));
+	element->value = value;
 
 	/* Prevent concurrent inserts when likely updating entry point */
 	if (entryPoint == NULL || element->level > entryPoint->level)
@@ -593,11 +612,11 @@ HnswInsertTupleOnDisk(Relation index, Datum value, Datum *values, bool *isnull,
 		entryPoint = HnswGetEntryPoint(index);
 	}
 
-	/* Find neighbors for element */
+	/* Insert element in graph */
-	HnswFindElementNeighbors(base, element, entryPoint, index, procinfo, collation, m, efConstruction, false);
+	HnswInsertElement(element, entryPoint, index, procinfo, collation, m, efConstruction, false);
 
-	/* Update graph on disk */
+	/* Write to disk */
-	UpdateGraphOnDisk(index, procinfo, collation, element, m, efConstruction, entryPoint, building);
+	WriteElement(index, procinfo, collation, element, m, efConstruction, entryPoint, building);
 
 	/* Release lock */
 	UnlockPage(index, HNSW_UPDATE_LOCK, lockmode);
@@ -605,30 +624,6 @@ HnswInsertTupleOnDisk(Relation index, Datum value, Datum *values, bool *isnull,
 	return true;
 }
 
-/*
- * Insert a tuple into the index
- */
-static void
-HnswInsertTuple(Relation index, Datum *values, bool *isnull, ItemPointer heap_tid)
-{
-	Datum		value;
-	FmgrInfo   *normprocinfo;
-	Oid			collation = index->rd_indcollation[0];
-
-	/* Detoast once for all calls */
-	value = PointerGetDatum(PG_DETOAST_DATUM(values[0]));
-
-	/* Normalize if needed */
-	normprocinfo = HnswOptionalProcInfo(index, HNSW_NORM_PROC);
-	if (normprocinfo != NULL)
-	{
-		if (!HnswNormValue(normprocinfo, collation, &value, NULL))
-			return;
-	}
-
-	HnswInsertTupleOnDisk(index, value, values, isnull, heap_tid, false);
-}
-
 /*
  * Insert a tuple into the index
  */
@@ -655,7 +650,7 @@ hnswinsert(Relation index, Datum *values, bool *isnull, ItemPointer heap_tid,
 	oldCtx = MemoryContextSwitchTo(insertCtx);
 
 	/* Insert tuple */
-	HnswInsertTuple(index, values, isnull, heap_tid);
+	HnswInsertTuple(index, values, isnull, heap_tid, heap, false);
 
 	/* Delete memory context */
 	MemoryContextSwitchTo(oldCtx);

src/hnswscan.c

@@ -21,7 +21,6 @@ GetScanItems(IndexScanDesc scan, Datum q)
 	List	   *w;
 	int			m;
 	HnswElement entryPoint;
-	char	   *base = NULL;
 
 	/* Get m and entry point */
 	HnswGetMetaPageInfo(index, &m, &entryPoint);
@@ -29,15 +28,15 @@ GetScanItems(IndexScanDesc scan, Datum q)
 	if (entryPoint == NULL)
 		return NIL;
 
-	ep = list_make1(HnswEntryCandidate(base, entryPoint, q, index, procinfo, collation, false));
+	ep = list_make1(HnswEntryCandidate(entryPoint, q, index, procinfo, collation, false));
 
 	for (int lc = entryPoint->level; lc >= 1; lc--)
 	{
-		w = HnswSearchLayer(base, q, ep, 1, lc, index, procinfo, collation, m, false, NULL);
+		w = HnswSearchLayer(q, ep, 1, lc, index, procinfo, collation, m, false, NULL);
 		ep = w;
 	}
 
-	return HnswSearchLayer(base, q, ep, hnsw_ef_search, 0, index, procinfo, collation, m, false, NULL);
+	return HnswSearchLayer(q, ep, hnsw_ef_search, 0, index, procinfo, collation, m, false, NULL);
 }
 
 /*
@@ -185,24 +184,26 @@ hnswgettuple(IndexScanDesc scan, ScanDirection dir)
 
 	while (list_length(so->w) > 0)
 	{
-		char	   *base = NULL;
 		HnswCandidate *hc = llast(so->w);
-		HnswElement element = HnswPtrAccess(base, hc->element);
 		ItemPointer heaptid;
 
 		/* Move to next element if no valid heap TIDs */
-		if (element->heaptidsLength == 0)
+		if (hc->element->heaptidsLength == 0)
 		{
 			so->w = list_delete_last(so->w);
 			continue;
 		}
 
-		heaptid = &element->heaptids[--element->heaptidsLength];
+		heaptid = &hc->element->heaptids[--hc->element->heaptidsLength];
 
 		MemoryContextSwitchTo(oldCtx);
 
+#if PG_VERSION_NUM >= 120000
 		scan->xs_heaptid = *heaptid;
-		scan->xs_recheck = false;
+#else
+		scan->xs_ctup.t_self = *heaptid;
+#endif
+
 		scan->xs_recheckorderby = false;
 		return true;
 	}

src/hnswutils.c

@@ -2,13 +2,9 @@
 
 #include <math.h>
 
-#include "access/generic_xlog.h"
 #include "hnsw.h"
-#include "lib/pairingheap.h"
 #include "storage/bufmgr.h"
 #include "utils/datum.h"
-#include "utils/memdebug.h"
-#include "utils/rel.h"
 #include "vector.h"
 
 #if PG_VERSION_NUM >= 130000
@@ -60,6 +56,13 @@ hash_tid(ItemPointerData tid)
 #define SH_DEFINE
 #include "lib/simplehash.h"
 
+/* Needed to include simplehash.h twice */
+#if PG_VERSION_NUM < 120000
+#undef SH_EQUAL
+#define sh_log2 pointerhash_sh_log2
+#define sh_pow2 pointerhash_sh_pow2
+#endif
+
 /* Pointer hash table */
 static uint32
 hash_pointer(uintptr_t ptr)
@@ -81,31 +84,9 @@ hash_pointer(uintptr_t ptr)
 #define SH_DEFINE
 #include "lib/simplehash.h"
 
-/* Offset hash table */
-static uint32
-hash_offset(Size offset)
-{
-#if SIZEOF_SIZE_T == 8
-	return murmurhash64((uint64) offset);
-#else
-	return murmurhash32((uint32) offset);
-#endif
-}
-
-#define SH_PREFIX		offsethash
-#define SH_ELEMENT_TYPE	OffsetHashEntry
-#define SH_KEY_TYPE		Size
-#define	SH_KEY			offset
-#define SH_HASH_KEY(tb, key)	hash_offset(key)
-#define SH_EQUAL(tb, a, b)		(a == b)
-#define	SH_SCOPE		extern
-#define SH_DEFINE
-#include "lib/simplehash.h"
-
 typedef union
 {
 	pointerhash_hash *pointers;
-	offsethash_hash *offsets;
 	tidhash_hash *tids;
 }			visited_hash;
 
@@ -203,53 +184,35 @@ HnswInitPage(Buffer buf, Page page)
 	HnswPageGetOpaque(page)->page_id = HNSW_PAGE_ID;
 }
 
-/*
- * Allocate a neighbor array
- */
-static HnswNeighborArray *
-HnswInitNeighborArray(int lm, HnswAllocator * allocator)
-{
-	HnswNeighborArray *a = HnswAlloc(allocator, HNSW_NEIGHBOR_ARRAY_SIZE(lm));
-
-	a->length = 0;
-	a->closerSet = false;
-	return a;
-}
-
 /*
  * Allocate neighbors
  */
 void
-HnswInitNeighbors(char *base, HnswElement element, int m, HnswAllocator * allocator)
+HnswInitNeighbors(HnswElement element, int m)
 {
 	int			level = element->level;
-	HnswNeighborArrayPtr *neighborList = (HnswNeighborArrayPtr *) HnswAlloc(allocator, sizeof(HnswNeighborArrayPtr) * (level + 1));
 
-	HnswPtrStore(base, element->neighbors, neighborList);
+	element->neighbors = palloc(sizeof(HnswNeighborArray) * (level + 1));
 
 	for (int lc = 0; lc <= level; lc++)
-		HnswPtrStore(base, neighborList[lc], HnswInitNeighborArray(HnswGetLayerM(m, lc), allocator));
+	{
-}
+		HnswNeighborArray *a;
+		int			lm = HnswGetLayerM(m, lc);
 
-/*
+		a = &element->neighbors[lc];
- * Allocate memory from the allocator
+		a->length = 0;
- */
+		a->items = palloc(sizeof(HnswCandidate) * lm);
-void *
+		a->closerSet = false;
-HnswAlloc(HnswAllocator * allocator, Size size)
+	}
-{
-	if (allocator)
-		return (*(allocator)->alloc) (size, (allocator)->state);
-
-	return palloc(size);
 }
 
 /*
  * Allocate an element
  */
 HnswElement
-HnswInitElement(char *base, ItemPointer heaptid, int m, double ml, int maxLevel, HnswAllocator * allocator)
+HnswInitElement(ItemPointer heaptid, int m, double ml, int maxLevel)
 {
-	HnswElement element = HnswAlloc(allocator, sizeof(HnswElementData));
+	HnswElement element = palloc(sizeof(HnswElementData));
 
 	int			level = (int) (-log(RandomDouble()) * ml);
 
@@ -263,9 +226,9 @@ HnswInitElement(char *base, ItemPointer heaptid, int m, double ml, int maxLevel,
 	element->level = level;
 	element->deleted = 0;
 
-	HnswInitNeighbors(base, element, m, allocator);
+	HnswInitNeighbors(element, m);
 
-	HnswPtrStore(base, element->value, (Pointer) NULL);
+	element->value = PointerGetDatum(NULL);
 
 	return element;
 }
@@ -286,12 +249,11 @@ HnswElement
 HnswInitElementFromBlock(BlockNumber blkno, OffsetNumber offno)
 {
 	HnswElement element = palloc(sizeof(HnswElementData));
-	char	   *base = NULL;
 
 	element->blkno = blkno;
 	element->offno = offno;
-	HnswPtrStore(base, element->neighbors, (HnswNeighborArrayPtr *) NULL);
+	element->neighbors = NULL;
-	HnswPtrStore(base, element->value, (Pointer) NULL);
+	element->value = PointerGetDatum(NULL);
 	return element;
 }
 
@@ -316,10 +278,7 @@ HnswGetMetaPageInfo(Relation index, int *m, HnswElement * entryPoint)
 	if (entryPoint != NULL)
 	{
 		if (BlockNumberIsValid(metap->entryBlkno))
-		{
 			*entryPoint = HnswInitElementFromBlock(metap->entryBlkno, metap->entryOffno);
-			(*entryPoint)->level = metap->entryLevel;
-		}
 		else
 			*entryPoint = NULL;
 	}
@@ -404,10 +363,8 @@ HnswUpdateMetaPage(Relation index, int updateEntry, HnswElement entryPoint, Bloc
  * Set element tuple, except for neighbor info
  */
 void
-HnswSetElementTuple(char *base, HnswElementTuple etup, HnswElement element)
+HnswSetElementTuple(HnswElementTuple etup, HnswElement element)
 {
-	Pointer		valuePtr = HnswPtrAccess(base, element->value);
-
 	etup->type = HNSW_ELEMENT_TUPLE_TYPE;
 	etup->level = element->level;
 	etup->deleted = 0;
@@ -418,14 +375,14 @@ HnswSetElementTuple(char *base, HnswElementTuple etup, HnswElement element)
 		else
 			ItemPointerSetInvalid(&etup->heaptids[i]);
 	}
-	memcpy(&etup->data, valuePtr, VARSIZE_ANY(valuePtr));
+	memcpy(&etup->data, DatumGetPointer(element->value), VARSIZE_ANY(DatumGetPointer(element->value)));
 }
 
 /*
  * Set neighbor tuple
  */
 void
-HnswSetNeighborTuple(char *base, HnswNeighborTuple ntup, HnswElement e, int m)
+HnswSetNeighborTuple(HnswNeighborTuple ntup, HnswElement e, int m)
 {
 	int			idx = 0;
 
@@ -433,7 +390,7 @@ HnswSetNeighborTuple(char *base, HnswNeighborTuple ntup, HnswElement e, int m)
 
 	for (int lc = e->level; lc >= 0; lc--)
 	{
-		HnswNeighborArray *neighbors = HnswGetNeighbors(base, e, lc);
+		HnswNeighborArray *neighbors = HnswGetNeighbors(e, lc);
 		int			lm = HnswGetLayerM(m, lc);
 
 		for (int i = 0; i < lm; i++)
@@ -443,9 +400,8 @@ HnswSetNeighborTuple(char *base, HnswNeighborTuple ntup, HnswElement e, int m)
 			if (i < neighbors->length)
 			{
 				HnswCandidate *hc = &neighbors->items[i];
-				HnswElement hce = HnswPtrAccess(base, hc->element);
 
-				ItemPointerSet(indextid, hce->blkno, hce->offno);
+				ItemPointerSet(indextid, hc->element->blkno, hc->element->offno);
 			}
 			else
 				ItemPointerSetInvalid(indextid);
@@ -461,14 +417,12 @@ HnswSetNeighborTuple(char *base, HnswNeighborTuple ntup, HnswElement e, int m)
 static void
 LoadNeighborsFromPage(HnswElement element, Relation index, Page page, int m)
 {
-	char	   *base = NULL;
-
 	HnswNeighborTuple ntup = (HnswNeighborTuple) PageGetItem(page, PageGetItemId(page, element->neighborOffno));
 	int			neighborCount = (element->level + 2) * m;
 
 	Assert(HnswIsNeighborTuple(ntup));
 
-	HnswInitNeighbors(base, element, m, NULL);
+	HnswInitNeighbors(element, m);
 
 	/* Ensure expected neighbors */
 	if (ntup->count != neighborCount)
@@ -494,9 +448,9 @@ LoadNeighborsFromPage(HnswElement element, Relation index, Page page, int m)
 		if (level < 0)
 			level = 0;
 
-		neighbors = HnswGetNeighbors(base, element, level);
+		neighbors = HnswGetNeighbors(element, level);
 		hc = &neighbors->items[neighbors->length++];
-		HnswPtrStore(base, hc->element, e);
+		hc->element = e;
 	}
 }
 
@@ -543,12 +497,7 @@ HnswLoadElementFromTuple(HnswElement element, HnswElementTuple etup, bool loadHe
 	}
 
 	if (loadVec)
-	{
+		element->value = datumCopy(PointerGetDatum(&etup->data), false, -1);
-		char	   *base = NULL;
-		Datum		value = datumCopy(PointerGetDatum(&etup->data), false, -1);
-
-		HnswPtrStore(base, element->value, DatumGetPointer(value));
-	}
 }
 
 /*
@@ -584,27 +533,24 @@ HnswLoadElement(HnswElement element, float *distance, Datum *q, Relation index,
  * Get the distance for a candidate
  */
 static float
-GetCandidateDistance(char *base, HnswCandidate * hc, Datum q, FmgrInfo *procinfo, Oid collation)
+GetCandidateDistance(HnswCandidate * hc, Datum q, FmgrInfo *procinfo, Oid collation)
 {
-	HnswElement hce = HnswPtrAccess(base, hc->element);
+	return DatumGetFloat8(FunctionCall2Coll(procinfo, collation, q, hc->element->value));
-	Datum		value = HnswGetValue(base, hce);
-
-	return DatumGetFloat8(FunctionCall2Coll(procinfo, collation, q, value));
 }
 
 /*
  * Create a candidate for the entry point
  */
 HnswCandidate *
-HnswEntryCandidate(char *base, HnswElement entryPoint, Datum q, Relation index, FmgrInfo *procinfo, Oid collation, bool loadVec)
+HnswEntryCandidate(HnswElement entryPoint, Datum q, Relation index, FmgrInfo *procinfo, Oid collation, bool loadVec)
 {
 	HnswCandidate *hc = palloc(sizeof(HnswCandidate));
 
-	HnswPtrStore(base, hc->element, entryPoint);
+	hc->element = entryPoint;
 	if (index == NULL)
-		hc->distance = GetCandidateDistance(base, hc, q, procinfo, collation);
+		hc->distance = GetCandidateDistance(hc, q, procinfo, collation);
 	else
-		HnswLoadElement(entryPoint, &hc->distance, &q, index, procinfo, collation, loadVec);
+		HnswLoadElement(hc->element, &hc->distance, &q, index, procinfo, collation, loadVec);
 	return hc;
 }
 
@@ -650,79 +596,34 @@ CreatePairingHeapNode(HnswCandidate * c)
 	return node;
 }
 
-/*
- * Init visited
- */
-static inline void
-InitVisited(char *base, visited_hash * v, Relation index, int ef, int m)
-{
-	if (index != NULL)
-		v->tids = tidhash_create(CurrentMemoryContext, ef * m * 2, NULL);
-	else if (base != NULL)
-		v->offsets = offsethash_create(CurrentMemoryContext, ef * m * 2, NULL);
-	else
-		v->pointers = pointerhash_create(CurrentMemoryContext, ef * m * 2, NULL);
-}
-
 /*
  * Add to visited
  */
 static inline void
-AddToVisited(char *base, visited_hash * v, HnswCandidate * hc, Relation index, bool *found)
+AddToVisited(visited_hash v, HnswCandidate * hc, Relation index, bool *found)
 {
-	if (index != NULL)
+	if (index == NULL)
-	{
-		HnswElement element = HnswPtrAccess(base, hc->element);
-		ItemPointerData indextid;
-
-		ItemPointerSet(&indextid, element->blkno, element->offno);
-		tidhash_insert(v->tids, indextid, found);
-	}
-	else if (base != NULL)
 	{
 #if PG_VERSION_NUM >= 130000
-		HnswElement element = HnswPtrAccess(base, hc->element);
+		pointerhash_insert_hash(v.pointers, (uintptr_t) hc->element, hc->element->hash, found);
-
-		offsethash_insert_hash(v->offsets, HnswPtrOffset(hc->element), element->hash, found);
 #else
-		offsethash_insert(v->offsets, HnswPtrOffset(hc->element), found);
+		pointerhash_insert(v.pointers, (uintptr_t) hc->element, found);
 #endif
 	}
 	else
 	{
-#if PG_VERSION_NUM >= 130000
+		ItemPointerData indextid;
-		HnswElement element = HnswPtrAccess(base, hc->element);
 
-		pointerhash_insert_hash(v->pointers, (uintptr_t) HnswPtrPointer(hc->element), element->hash, found);
+		ItemPointerSet(&indextid, hc->element->blkno, hc->element->offno);
-#else
+		tidhash_insert(v.tids, indextid, found);
-		pointerhash_insert(v->pointers, (uintptr_t) HnswPtrPointer(hc->element), found);
-#endif
 	}
 }
 
-/*
- * Count element towards ef
- */
-static inline bool
-CountElement(char *base, HnswElement skipElement, HnswCandidate * hc)
-{
-	HnswElement e;
-
-	if (skipElement == NULL)
-		return true;
-
-	/* Ensure does not access heaptidsLength during in-memory build */
-	pg_memory_barrier();
-
-	e = HnswPtrAccess(base, hc->element);
-	return e->heaptidsLength != 0;
-}
-
 /*
  * Algorithm 2 from paper
  */
 List *
-HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, FmgrInfo *procinfo, Oid collation, int m, bool inserting, HnswElement skipElement)
+HnswSearchLayer(Datum q, List *ep, int ef, int lc, Relation index, FmgrInfo *procinfo, Oid collation, int m, bool inserting, HnswElement skipElement)
 {
 	List	   *w = NIL;
 	pairingheap *C = pairingheap_allocate(CompareNearestCandidates, NULL);
@@ -730,17 +631,12 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 	int			wlen = 0;
 	visited_hash v;
 	ListCell   *lc2;
-	HnswNeighborArray *neighborhoodData = NULL;
-	Size		neighborhoodSize;
 
-	InitVisited(base, &v, index, ef, m);
+	/* Create hash table */
-
-	/* Create local memory for neighborhood if needed */
 	if (index == NULL)
-	{
+		v.pointers = pointerhash_create(CurrentMemoryContext, ef * m * 2, NULL);
-		neighborhoodSize = HNSW_NEIGHBOR_ARRAY_SIZE(HnswGetLayerM(m, lc));
+	else
-		neighborhoodData = palloc(neighborhoodSize);
+		v.tids = tidhash_create(CurrentMemoryContext, ef * m * 2, NULL);
-	}
 
 	/* Add entry points to v, C, and W */
 	foreach(lc2, ep)
@@ -748,7 +644,7 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 		HnswCandidate *hc = (HnswCandidate *) lfirst(lc2);
 		bool		found;
 
-		AddToVisited(base, &v, hc, index, &found);
+		AddToVisited(v, hc, index, &found);
 
 		pairingheap_add(C, &(CreatePairingHeapNode(hc)->ph_node));
 		pairingheap_add(W, &(CreatePairingHeapNode(hc)->ph_node));
@@ -758,7 +654,7 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 		 * would be ideal to do this for inserts as well, but this could
 		 * affect insert performance.
 		 */
-		if (CountElement(base, skipElement, hc))
+		if (skipElement == NULL || hc->element->heaptidsLength != 0)
 			wlen++;
 	}
 
@@ -767,51 +663,38 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 		HnswNeighborArray *neighborhood;
 		HnswCandidate *c = ((HnswPairingHeapNode *) pairingheap_remove_first(C))->inner;
 		HnswCandidate *f = ((HnswPairingHeapNode *) pairingheap_first(W))->inner;
-		HnswElement cElement;
 
 		if (c->distance > f->distance)
 			break;
 
-		cElement = HnswPtrAccess(base, c->element);
+		if (c->element->neighbors == NULL)
-
+			HnswLoadNeighbors(c->element, index, m);
-		if (HnswPtrIsNull(base, cElement->neighbors))
-			HnswLoadNeighbors(cElement, index, m);
 
 		/* Get the neighborhood at layer lc */
-		neighborhood = HnswGetNeighbors(base, cElement, lc);
+		neighborhood = HnswGetNeighbors(c->element, lc);
-
-		/* Copy neighborhood to local memory if needed */
-		if (index == NULL)
-		{
-			LWLockAcquire(&cElement->lock, LW_SHARED);
-			memcpy(neighborhoodData, neighborhood, neighborhoodSize);
-			LWLockRelease(&cElement->lock);
-			neighborhood = neighborhoodData;
-		}
 
 		for (int i = 0; i < neighborhood->length; i++)
 		{
 			HnswCandidate *e = &neighborhood->items[i];
 			bool		visited;
 
-			AddToVisited(base, &v, e, index, &visited);
+			AddToVisited(v, e, index, &visited);
 
 			if (!visited)
 			{
 				float		eDistance;
-				HnswElement eElement = HnswPtrAccess(base, e->element);
 
 				f = ((HnswPairingHeapNode *) pairingheap_first(W))->inner;
 
 				if (index == NULL)
-					eDistance = GetCandidateDistance(base, e, q, procinfo, collation);
+					eDistance = GetCandidateDistance(e, q, procinfo, collation);
 				else
-					HnswLoadElement(eElement, &eDistance, &q, index, procinfo, collation, inserting);
+					HnswLoadElement(e->element, &eDistance, &q, index, procinfo, collation, inserting);
 
-				Assert(!eElement->deleted);
+				Assert(!e->element->deleted);
 
 				/* Make robust to issues */
-				if (eElement->level < lc)
+				if (e->element->level < lc)
 					continue;
 
 				if (eDistance < f->distance || wlen < ef)
@@ -819,7 +702,7 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 					/* Copy e */
 					HnswCandidate *ec = palloc(sizeof(HnswCandidate));
 
-					HnswPtrStore(base, ec->element, eElement);
+					ec->element = e->element;
 					ec->distance = eDistance;
 
 					pairingheap_add(C, &(CreatePairingHeapNode(ec)->ph_node));
@@ -830,7 +713,7 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 					 * vacuuming. It would be ideal to do this for inserts as
 					 * well, but this could affect insert performance.
 					 */
-					if (CountElement(base, skipElement, e))
+					if (skipElement == NULL || e->element->heaptidsLength != 0)
 					{
 						wlen++;
 
@@ -855,7 +738,7 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 }
 
 /*
- * Compare candidate distances with pointer tie-breaker
+ * Compare candidate distances
  */
 static int
 #if PG_VERSION_NUM >= 130000
@@ -873,38 +756,10 @@ CompareCandidateDistances(const void *a, const void *b)
 	if (hca->distance > hcb->distance)
 		return -1;
 
-	if (HnswPtrPointer(hca->element) < HnswPtrPointer(hcb->element))
+	if (hca->element < hcb->element)
 		return 1;
 
-	if (HnswPtrPointer(hca->element) > HnswPtrPointer(hcb->element))
+	if (hca->element > hcb->element)
-		return -1;
-
-	return 0;
-}
-
-/*
- * Compare candidate distances with offset tie-breaker
- */
-static int
-#if PG_VERSION_NUM >= 130000
-CompareCandidateDistancesOffset(const ListCell *a, const ListCell *b)
-#else
-CompareCandidateDistancesOffset(const void *a, const void *b)
-#endif
-{
-	HnswCandidate *hca = lfirst((ListCell *) a);
-	HnswCandidate *hcb = lfirst((ListCell *) b);
-
-	if (hca->distance < hcb->distance)
-		return 1;
-
-	if (hca->distance > hcb->distance)
-		return -1;
-
-	if (HnswPtrOffset(hca->element) < HnswPtrOffset(hcb->element))
-		return 1;
-
-	if (HnswPtrOffset(hca->element) > HnswPtrOffset(hcb->element))
 		return -1;
 
 	return 0;
@@ -914,28 +769,46 @@ CompareCandidateDistancesOffset(const void *a, const void *b)
  * Calculate the distance between elements
  */
 static float
-HnswGetDistance(char *base, HnswElement a, HnswElement b, FmgrInfo *procinfo, Oid collation)
+HnswGetDistance(HnswElement a, HnswElement b, int lc, FmgrInfo *procinfo, Oid collation)
 {
-	Datum		aValue = HnswGetValue(base, a);
+	/* Look for cached distance */
-	Datum		bValue = HnswGetValue(base, b);
+	if (a->neighbors != NULL)
+	{
+		HnswNeighborArray *neighbors = HnswGetNeighbors(a, lc);
 
-	return DatumGetFloat8(FunctionCall2Coll(procinfo, collation, aValue, bValue));
+		for (int i = 0; i < neighbors->length; i++)
+		{
+			if (neighbors->items[i].element == b)
+				return neighbors->items[i].distance;
+		}
+	}
+
+	if (b->neighbors != NULL)
+	{
+		HnswNeighborArray *neighbors = HnswGetNeighbors(b, lc);
+
+		for (int i = 0; i < neighbors->length; i++)
+		{
+			if (neighbors->items[i].element == a)
+				return neighbors->items[i].distance;
+		}
+	}
+
+	return DatumGetFloat8(FunctionCall2Coll(procinfo, collation, a->value, b->value));
 }
 
 /*
  * Check if an element is closer to q than any element from R
  */
 static bool
-CheckElementCloser(char *base, HnswCandidate * e, List *r, FmgrInfo *procinfo, Oid collation)
+CheckElementCloser(HnswCandidate * e, List *r, int lc, FmgrInfo *procinfo, Oid collation)
 {
-	HnswElement eElement = HnswPtrAccess(base, e->element);
 	ListCell   *lc2;
 
 	foreach(lc2, r)
 	{
 		HnswCandidate *ri = lfirst(lc2);
-		HnswElement riElement = HnswPtrAccess(base, ri->element);
+		float		distance = HnswGetDistance(e->element, ri->element, lc, procinfo, collation);
-		float		distance = HnswGetDistance(base, eElement, riElement, procinfo, collation);
 
 		if (distance <= e->distance)
 			return false;
@@ -948,31 +821,26 @@ CheckElementCloser(char *base, HnswCandidate * e, List *r, FmgrInfo *procinfo, O
  * Algorithm 4 from paper
  */
 static List *
-SelectNeighbors(char *base, List *c, int lm, int lc, FmgrInfo *procinfo, Oid collation, HnswElement e2, HnswCandidate * newCandidate, HnswCandidate * *pruned, bool sortCandidates)
+SelectNeighbors(List *c, int m, int lc, FmgrInfo *procinfo, Oid collation, HnswElement e2, HnswCandidate * newCandidate, HnswCandidate * *pruned, bool sortCandidates)
 {
 	List	   *r = NIL;
 	List	   *w = list_copy(c);
 	pairingheap *wd;
-	HnswNeighborArray *neighbors = HnswGetNeighbors(base, e2, lc);
+	HnswNeighborArray *neighbors = HnswGetNeighbors(e2, lc);
 	bool		mustCalculate = !neighbors->closerSet;
 	List	   *added = NIL;
 	bool		removedAny = false;
 
-	if (list_length(w) <= lm)
+	if (list_length(w) <= m)
 		return w;
 
 	wd = pairingheap_allocate(CompareNearestCandidates, NULL);
 
 	/* Ensure order of candidates is deterministic for closer caching */
 	if (sortCandidates)
-	{
+		list_sort(w, CompareCandidateDistances);
-		if (base == NULL)
-			list_sort(w, CompareCandidateDistances);
-		else
-			list_sort(w, CompareCandidateDistancesOffset);
-	}
 
-	while (list_length(w) > 0 && list_length(r) < lm)
+	while (list_length(w) > 0 && list_length(r) < m)
 	{
 		/* Assumes w is already ordered desc */
 		HnswCandidate *e = llast(w);
@@ -981,20 +849,16 @@ SelectNeighbors(char *base, List *c, int lm, int lc, FmgrInfo *procinfo, Oid col
 
 		/* Use previous state of r and wd to skip work when possible */
 		if (mustCalculate)
-			e->closer = CheckElementCloser(base, e, r, procinfo, collation);
+			e->closer = CheckElementCloser(e, r, lc, procinfo, collation);
 		else if (list_length(added) > 0)
 		{
-			/* Keep Valgrind happy for in-memory, parallel builds */
-			if (base != NULL)
-				VALGRIND_MAKE_MEM_DEFINED(&e->closer, 1);
-
 			/*
 			 * If the current candidate was closer, we only need to compare it
 			 * with the other candidates that we have added.
 			 */
 			if (e->closer)
 			{
-				e->closer = CheckElementCloser(base, e, added, procinfo, collation);
+				e->closer = CheckElementCloser(e, added, lc, procinfo, collation);
 
 				if (!e->closer)
 					removedAny = true;
@@ -1007,7 +871,7 @@ SelectNeighbors(char *base, List *c, int lm, int lc, FmgrInfo *procinfo, Oid col
 				 */
 				if (removedAny)
 				{
-					e->closer = CheckElementCloser(base, e, r, procinfo, collation);
+					e->closer = CheckElementCloser(e, r, lc, procinfo, collation);
 					if (e->closer)
 						added = lappend(added, e);
 				}
@@ -1015,15 +879,11 @@ SelectNeighbors(char *base, List *c, int lm, int lc, FmgrInfo *procinfo, Oid col
 		}
 		else if (e == newCandidate)
 		{
-			e->closer = CheckElementCloser(base, e, r, procinfo, collation);
+			e->closer = CheckElementCloser(e, r, lc, procinfo, collation);
 			if (e->closer)
 				added = lappend(added, e);
 		}
 
-		/* Keep Valgrind happy for in-memory, parallel builds */
-		if (base != NULL)
-			VALGRIND_MAKE_MEM_DEFINED(&e->closer, 1);
-
 		if (e->closer)
 			r = lappend(r, e);
 		else
@@ -1034,7 +894,7 @@ SelectNeighbors(char *base, List *c, int lm, int lc, FmgrInfo *procinfo, Oid col
 	neighbors->closerSet = sortCandidates;
 
 	/* Keep pruned connections */
-	while (!pairingheap_is_empty(wd) && list_length(r) < lm)
+	while (!pairingheap_is_empty(wd) && list_length(r) < m)
 		r = lappend(r, ((HnswPairingHeapNode *) pairingheap_remove_first(wd))->inner);
 
 	/* Return pruned for update connections */
@@ -1053,10 +913,10 @@ SelectNeighbors(char *base, List *c, int lm, int lc, FmgrInfo *procinfo, Oid col
  * Add connections
  */
 static void
-AddConnections(char *base, HnswElement element, List *neighbors, int lc)
+AddConnections(HnswElement element, List *neighbors, int m, int lc)
 {
 	ListCell   *lc2;
-	HnswNeighborArray *a = HnswGetNeighbors(base, element, lc);
+	HnswNeighborArray *a = HnswGetNeighbors(element, lc);
 
 	foreach(lc2, neighbors)
 		a->items[a->length++] = *((HnswCandidate *) lfirst(lc2));
@@ -1066,16 +926,16 @@ AddConnections(char *base, HnswElement element, List *neighbors, int lc)
  * Update connections
  */
 void
-HnswUpdateConnection(char *base, HnswElement element, HnswCandidate * hc, int lm, int lc, int *updateIdx, Relation index, FmgrInfo *procinfo, Oid collation)
+HnswUpdateConnection(HnswElement element, HnswCandidate * hc, int m, int lc, int *updateIdx, Relation index, FmgrInfo *procinfo, Oid collation)
 {
-	HnswElement hce = HnswPtrAccess(base, hc->element);
+	HnswNeighborArray *currentNeighbors = HnswGetNeighbors(hc->element, lc);
-	HnswNeighborArray *currentNeighbors = HnswGetNeighbors(base, hce, lc);
+
 	HnswCandidate hc2;
 
-	HnswPtrStore(base, hc2.element, element);
+	hc2.element = element;
 	hc2.distance = hc->distance;
 
-	if (currentNeighbors->length < lm)
+	if (currentNeighbors->length < m)
 	{
 		currentNeighbors->items[currentNeighbors->length++] = hc2;
 
@@ -1091,20 +951,19 @@ HnswUpdateConnection(char *base, HnswElement element, HnswCandidate * hc, int lm
 		/* Load elements on insert */
 		if (index != NULL)
 		{
-			Datum		q = HnswGetValue(base, hce);
+			Datum		q = hc->element->value;
 
 			for (int i = 0; i < currentNeighbors->length; i++)
 			{
 				HnswCandidate *hc3 = &currentNeighbors->items[i];
-				HnswElement hc3Element = HnswPtrAccess(base, hc3->element);
 
-				if (HnswPtrIsNull(base, hc3Element->value))
+				if (DatumGetPointer(hc3->element->value) == NULL)
-					HnswLoadElement(hc3Element, &hc3->distance, &q, index, procinfo, collation, true);
+					HnswLoadElement(hc3->element, &hc3->distance, &q, index, procinfo, collation, true);
 				else
-					hc3->distance = GetCandidateDistance(base, hc3, q, procinfo, collation);
+					hc3->distance = GetCandidateDistance(hc3, q, procinfo, collation);
 
 				/* Prune element if being deleted */
-				if (hc3Element->heaptidsLength == 0)
+				if (hc3->element->heaptidsLength == 0)
 				{
 					pruned = &currentNeighbors->items[i];
 					break;
@@ -1121,7 +980,7 @@ HnswUpdateConnection(char *base, HnswElement element, HnswCandidate * hc, int lm
 				c = lappend(c, &currentNeighbors->items[i]);
 			c = lappend(c, &hc2);
 
-			SelectNeighbors(base, c, lm, lc, procinfo, collation, hce, &hc2, &pruned, true);
+			SelectNeighbors(c, m, lc, procinfo, collation, hc->element, &hc2, &pruned, true);
 
 			/* Should not happen */
 			if (pruned == NULL)
@@ -1131,7 +990,7 @@ HnswUpdateConnection(char *base, HnswElement element, HnswCandidate * hc, int lm
 		/* Find and replace the pruned element */
 		for (int i = 0; i < currentNeighbors->length; i++)
 		{
-			if (HnswPtrEqual(base, currentNeighbors->items[i].element, pruned->element))
+			if (currentNeighbors->items[i].element == pruned->element)
 			{
 				currentNeighbors->items[i] = hc2;
 
@@ -1149,65 +1008,43 @@ HnswUpdateConnection(char *base, HnswElement element, HnswCandidate * hc, int lm
  * Remove elements being deleted or skipped
  */
 static List *
-RemoveElements(char *base, List *w, HnswElement skipElement)
+RemoveElements(List *w, HnswElement skipElement)
 {
 	ListCell   *lc2;
 	List	   *w2 = NIL;
 
-	/* Ensure does not access heaptidsLength during in-memory build */
-	pg_memory_barrier();
-
 	foreach(lc2, w)
 	{
 		HnswCandidate *hc = (HnswCandidate *) lfirst(lc2);
-		HnswElement hce = HnswPtrAccess(base, hc->element);
 
 		/* Skip self for vacuuming update */
-		if (skipElement != NULL && hce->blkno == skipElement->blkno && hce->offno == skipElement->offno)
+		if (skipElement != NULL && hc->element->blkno == skipElement->blkno && hc->element->offno == skipElement->offno)
 			continue;
 
-		if (hce->heaptidsLength != 0)
+		if (hc->element->heaptidsLength != 0)
 			w2 = lappend(w2, hc);
 	}
 
 	return w2;
 }
 
-#if PG_VERSION_NUM >= 130000
-/*
- * Precompute hash
- */
-static void
-PrecomputeHash(char *base, HnswElement element)
-{
-	HnswElementPtr ptr;
-
-	HnswPtrStore(base, ptr, element);
-
-	if (base == NULL)
-		element->hash = hash_pointer((uintptr_t) HnswPtrPointer(ptr));
-	else
-		element->hash = hash_offset(HnswPtrOffset(ptr));
-}
-#endif
-
 /*
  * Algorithm 1 from paper
  */
 void
-HnswFindElementNeighbors(char *base, HnswElement element, HnswElement entryPoint, Relation index, FmgrInfo *procinfo, Oid collation, int m, int efConstruction, bool existing)
+HnswInsertElement(HnswElement element, HnswElement entryPoint, Relation index, FmgrInfo *procinfo, Oid collation, int m, int efConstruction, bool existing)
 {
 	List	   *ep;
 	List	   *w;
 	int			level = element->level;
 	int			entryLevel;
-	Datum		q = HnswGetValue(base, element);
+	Datum		q = element->value;
 	HnswElement skipElement = existing ? element : NULL;
 
 #if PG_VERSION_NUM >= 130000
 	/* Precompute hash */
 	if (index == NULL)
-		PrecomputeHash(base, element);
+		element->hash = hash_pointer((uintptr_t) element);
 #endif
 
 	/* No neighbors if no entry point */
@@ -1215,13 +1052,13 @@ HnswFindElementNeighbors(char *base, HnswElement element, HnswElement entryPoint
 		return;
 
 	/* Get entry point and level */
-	ep = list_make1(HnswEntryCandidate(base, entryPoint, q, index, procinfo, collation, true));
+	ep = list_make1(HnswEntryCandidate(entryPoint, q, index, procinfo, collation, true));
 	entryLevel = entryPoint->level;
 
 	/* 1st phase: greedy search to insert level */
 	for (int lc = entryLevel; lc >= level + 1; lc--)
 	{
-		w = HnswSearchLayer(base, q, ep, 1, lc, index, procinfo, collation, m, true, skipElement);
+		w = HnswSearchLayer(q, ep, 1, lc, index, procinfo, collation, m, true, skipElement);
 		ep = w;
 	}
 
@@ -1239,12 +1076,12 @@ HnswFindElementNeighbors(char *base, HnswElement element, HnswElement entryPoint
 		List	   *neighbors;
 		List	   *lw;
 
-		w = HnswSearchLayer(base, q, ep, efConstruction, lc, index, procinfo, collation, m, true, skipElement);
+		w = HnswSearchLayer(q, ep, efConstruction, lc, index, procinfo, collation, m, true, skipElement);
 
 		/* Elements being deleted or skipped can help with search */
 		/* but should be removed before selecting neighbors */
 		if (index != NULL)
-			lw = RemoveElements(base, w, skipElement);
+			lw = RemoveElements(w, skipElement);
 		else
 			lw = w;
 
@@ -1253,9 +1090,9 @@ HnswFindElementNeighbors(char *base, HnswElement element, HnswElement entryPoint
 		 * sortCandidates to true for in-memory builds to enable closer
 		 * caching, but there does not seem to be a difference in performance.
 		 */
-		neighbors = SelectNeighbors(base, lw, lm, lc, procinfo, collation, element, NULL, NULL, false);
+		neighbors = SelectNeighbors(lw, lm, lc, procinfo, collation, element, NULL, NULL, false);
 
-		AddConnections(base, element, neighbors, lc);
+		AddConnections(element, neighbors, lm, lc);
 
 		ep = w;
 	}

src/hnswvacuum.c

@@ -2,7 +2,6 @@
 
 #include <math.h>
 
-#include "access/generic_xlog.h"
 #include "commands/vacuum.h"
 #include "hnsw.h"
 #include "storage/bufmgr.h"
@@ -60,7 +59,8 @@ RemoveHeapTids(HnswVacuumState * vacuumstate)
 		/* Iterate over nodes */
 		for (offno = FirstOffsetNumber; offno <= maxoffno; offno = OffsetNumberNext(offno))
 		{
-			HnswElementTuple etup = (HnswElementTuple) PageGetItem(page, PageGetItemId(page, offno));
+			ItemId		itemid = PageGetItemId(page, offno);
+			HnswElementTuple etup = (HnswElementTuple) PageGetItem(page, itemid);
 			int			idx = 0;
 			bool		itemUpdated = false;
 
@@ -91,10 +91,15 @@ RemoveHeapTids(HnswVacuumState * vacuumstate)
 
 				if (itemUpdated)
 				{
+					Size		etupSize = ItemIdGetLength(itemid);
+
 					/* Mark rest as invalid */
 					for (int i = idx; i < HNSW_HEAPTIDS; i++)
 						ItemPointerSetInvalid(&etup->heaptids[i]);
 
+					if (!PageIndexTupleOverwrite(page, offno, (Item) etup, etupSize))
+						elog(ERROR, "failed to add index item to \"%s\"", RelationGetRelationName(index));
+
 					updated = true;
 				}
 			}
@@ -194,25 +199,21 @@ RepairGraphElement(HnswVacuumState * vacuumstate, HnswElement element, HnswEleme
 	BufferAccessStrategy bas = vacuumstate->bas;
 	HnswNeighborTuple ntup = vacuumstate->ntup;
 	Size		ntupSize = HNSW_NEIGHBOR_TUPLE_SIZE(element->level, m);
-	char	   *base = NULL;
 
 	/* Skip if element is entry point */
 	if (entryPoint != NULL && element->blkno == entryPoint->blkno && element->offno == entryPoint->offno)
 		return;
 
 	/* Init fields */
-	HnswInitNeighbors(base, element, m, NULL);
+	HnswInitNeighbors(element, m);
 	element->heaptidsLength = 0;
 
-	/* Find neighbors for element, skipping itself */
+	/* Add element to graph, skipping itself */
-	HnswFindElementNeighbors(base, element, entryPoint, index, procinfo, collation, m, efConstruction, true);
+	HnswInsertElement(element, entryPoint, index, procinfo, collation, m, efConstruction, true);
-
-	/* Zero memory for each element */
-	MemSet(ntup, 0, HNSW_TUPLE_ALLOC_SIZE);
 
 	/* Update neighbor tuple */
 	/* Do this before getting page to minimize locking */
-	HnswSetNeighborTuple(base, ntup, element, m);
+	HnswSetNeighborTuple(ntup, element, m);
 
 	/* Get neighbor page */
 	buf = ReadBufferExtended(index, MAIN_FORKNUM, element->neighborPage, RBM_NORMAL, bas);
@@ -229,7 +230,7 @@ RepairGraphElement(HnswVacuumState * vacuumstate, HnswElement element, HnswEleme
 	UnlockReleaseBuffer(buf);
 
 	/* Update neighbors */
-	HnswUpdateNeighborsOnDisk(index, procinfo, collation, element, m, true, false);
+	HnswUpdateNeighborPages(index, procinfo, collation, element, m, true, false);
 }
 
 /*
@@ -300,7 +301,7 @@ RepairGraphEntryPoint(HnswVacuumState * vacuumstate)
 			{
 				/* Reset neighbors from previous update */
 				if (highestPoint != NULL)
-					HnswPtrStore((char *) NULL, highestPoint->neighbors, (HnswNeighborArrayPtr *) NULL);
+					highestPoint->neighbors = NULL;
 
 				RepairGraphElement(vacuumstate, entryPoint, highestPoint);
 			}
@@ -476,8 +477,11 @@ MarkDeleted(HnswVacuumState * vacuumstate)
 		/* Update element and neighbors together */
 		for (offno = FirstOffsetNumber; offno <= maxoffno; offno = OffsetNumberNext(offno))
 		{
-			HnswElementTuple etup = (HnswElementTuple) PageGetItem(page, PageGetItemId(page, offno));
+			ItemId		itemid = PageGetItemId(page, offno);
+			HnswElementTuple etup = (HnswElementTuple) PageGetItem(page, itemid);
 			HnswNeighborTuple ntup;
+			Size		etupSize;
+			Size		ntupSize;
 			Buffer		nbuf;
 			Page		npage;
 			BlockNumber neighborPage;
@@ -501,6 +505,10 @@ MarkDeleted(HnswVacuumState * vacuumstate)
 			if (ItemPointerIsValid(&etup->heaptids[0]))
 				continue;
 
+			/* Calculate sizes */
+			etupSize = ItemIdGetLength(itemid);
+			ntupSize = HNSW_NEIGHBOR_TUPLE_SIZE(etup->level, vacuumstate->m);
+
 			/* Get neighbor page */
 			neighborPage = ItemPointerGetBlockNumber(&etup->neighbortid);
 			neighborOffno = ItemPointerGetOffsetNumber(&etup->neighbortid);
@@ -527,10 +535,13 @@ MarkDeleted(HnswVacuumState * vacuumstate)
 			for (int i = 0; i < ntup->count; i++)
 				ItemPointerSetInvalid(&ntup->indextids[i]);
 
-			/*
+			/* Overwrite element tuple */
-			 * We modified the tuples in place, no need to call
+			if (!PageIndexTupleOverwrite(page, offno, (Item) etup, etupSize))
-			 * PageIndexTupleOverwrite
+				elog(ERROR, "failed to add index item to \"%s\"", RelationGetRelationName(index));
-			 */
+
+			/* Overwrite neighbor tuple */
+			if (!PageIndexTupleOverwrite(npage, neighborOffno, (Item) ntup, ntupSize))
+				elog(ERROR, "failed to add index item to \"%s\"", RelationGetRelationName(index));
 
 			/* Commit */
 			GenericXLogFinish(state);
@@ -575,7 +586,7 @@ InitVacuumState(HnswVacuumState * vacuumstate, IndexVacuumInfo *info, IndexBulkD
 	vacuumstate->bas = GetAccessStrategy(BAS_BULKREAD);
 	vacuumstate->procinfo = index_getprocinfo(index, 1, HNSW_DISTANCE_PROC);
 	vacuumstate->collation = index->rd_indcollation[0];
-	vacuumstate->ntup = palloc0(HNSW_TUPLE_ALLOC_SIZE);
+	vacuumstate->ntup = palloc0(BLCKSZ);
 	vacuumstate->tmpCtx = AllocSetContextCreate(CurrentMemoryContext,
 												"Hnsw vacuum temporary context",
 												ALLOCSET_DEFAULT_SIZES);

src/ivfbuild.c

@@ -2,38 +2,58 @@
 
 #include <float.h>
 
-#include "access/table.h"
-#include "access/tableam.h"
 #include "access/parallel.h"
 #include "access/xact.h"
 #include "catalog/index.h"
 #include "catalog/pg_operator_d.h"
 #include "catalog/pg_type_d.h"
-#include "commands/progress.h"
 #include "ivfflat.h"
 #include "miscadmin.h"
-#include "optimizer/optimizer.h"
 #include "storage/bufmgr.h"
 #include "tcop/tcopprot.h"
 #include "utils/memutils.h"
 
 #if PG_VERSION_NUM >= 140000
 #include "utils/backend_progress.h"
-#else
+#elif PG_VERSION_NUM >= 120000
 #include "pgstat.h"
 #endif
 
+#if PG_VERSION_NUM >= 120000
+#include "access/tableam.h"
+#include "commands/progress.h"
+#else
+#define PROGRESS_CREATEIDX_SUBPHASE 0
+#define PROGRESS_CREATEIDX_TUPLES_TOTAL 0
+#define PROGRESS_CREATEIDX_TUPLES_DONE 0
+#endif
+
 #if PG_VERSION_NUM >= 130000
 #define CALLBACK_ITEM_POINTER ItemPointer tid
 #else
 #define CALLBACK_ITEM_POINTER HeapTuple hup
 #endif
 
+#if PG_VERSION_NUM >= 120000
+#define UpdateProgress(index, val) pgstat_progress_update_param(index, val)
+#else
+#define UpdateProgress(index, val) ((void)val)
+#endif
+
 #if PG_VERSION_NUM >= 140000
 #include "utils/backend_status.h"
 #include "utils/wait_event.h"
 #endif
 
+#if PG_VERSION_NUM >= 120000
+#include "access/table.h"
+#include "optimizer/optimizer.h"
+#else
+#include "access/heapam.h"
+#include "optimizer/planner.h"
+#include "pgstat.h"
+#endif
+
 #define PARALLEL_KEY_IVFFLAT_SHARED		UINT64CONST(0xA000000000000001)
 #define PARALLEL_KEY_TUPLESORT			UINT64CONST(0xA000000000000002)
 #define PARALLEL_KEY_IVFFLAT_CENTERS	UINT64CONST(0xA000000000000003)
@@ -130,8 +150,13 @@ SampleRows(IvfflatBuildState * buildstate)
 	{
 		BlockNumber targblock = BlockSampler_Next(&buildstate->bs);
 
+#if PG_VERSION_NUM >= 120000
 		table_index_build_range_scan(buildstate->heap, buildstate->index, buildstate->indexInfo,
 									 false, true, false, targblock, 1, SampleCallback, (void *) buildstate, NULL);
+#else
+		IndexBuildHeapRangeScan(buildstate->heap, buildstate->index, buildstate->indexInfo,
+								false, true, targblock, 1, SampleCallback, (void *) buildstate, NULL);
+#endif
 	}
 }
 
@@ -257,12 +282,16 @@ InsertTuples(Relation index, IvfflatBuildState * buildstate, ForkNumber forkNum)
 	IndexTuple	itup = NULL;	/* silence compiler warning */
 	int64		inserted = 0;
 
+#if PG_VERSION_NUM >= 120000
 	TupleTableSlot *slot = MakeSingleTupleTableSlot(buildstate->tupdesc, &TTSOpsMinimalTuple);
+#else
+	TupleTableSlot *slot = MakeSingleTupleTableSlot(buildstate->tupdesc);
+#endif
 	TupleDesc	tupdesc = RelationGetDescr(index);
 
-	pgstat_progress_update_param(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_LOAD);
+	UpdateProgress(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_LOAD);
 
-	pgstat_progress_update_param(PROGRESS_CREATEIDX_TUPLES_TOTAL, buildstate->indtuples);
+	UpdateProgress(PROGRESS_CREATEIDX_TUPLES_TOTAL, buildstate->indtuples);
 
 	GetNextTuple(buildstate->sortstate, tupdesc, slot, &itup, &list);
 
@@ -298,7 +327,7 @@ InsertTuples(Relation index, IvfflatBuildState * buildstate, ForkNumber forkNum)
 
 			pfree(itup);
 
-			pgstat_progress_update_param(PROGRESS_CREATEIDX_TUPLES_DONE, ++inserted);
+			UpdateProgress(PROGRESS_CREATEIDX_TUPLES_DONE, ++inserted);
 
 			GetNextTuple(buildstate->sortstate, tupdesc, slot, &itup, &list);
 		}
@@ -346,12 +375,20 @@ InitBuildState(IvfflatBuildState * buildstate, Relation heap, Relation index, In
 		elog(ERROR, "dimensions must be greater than one for this opclass");
 
 	/* Create tuple description for sorting */
+#if PG_VERSION_NUM >= 120000
 	buildstate->tupdesc = CreateTemplateTupleDesc(3);
+#else
+	buildstate->tupdesc = CreateTemplateTupleDesc(3, false);
+#endif
 	TupleDescInitEntry(buildstate->tupdesc, (AttrNumber) 1, "list", INT4OID, -1, 0);
 	TupleDescInitEntry(buildstate->tupdesc, (AttrNumber) 2, "tid", TIDOID, -1, 0);
 	TupleDescInitEntry(buildstate->tupdesc, (AttrNumber) 3, "vector", RelationGetDescr(index)->attrs[0].atttypid, -1, 0);
 
+#if PG_VERSION_NUM >= 120000
 	buildstate->slot = MakeSingleTupleTableSlot(buildstate->tupdesc, &TTSOpsVirtual);
+#else
+	buildstate->slot = MakeSingleTupleTableSlot(buildstate->tupdesc);
+#endif
 
 	buildstate->centers = VectorArrayInit(buildstate->lists, buildstate->dimensions);
 	buildstate->listInfo = palloc(sizeof(ListInfo) * buildstate->lists);
@@ -398,7 +435,7 @@ ComputeCenters(IvfflatBuildState * buildstate)
 {
 	int			numSamples;
 
-	pgstat_progress_update_param(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_KMEANS);
+	UpdateProgress(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_KMEANS);
 
 	/* Target 50 samples per list, with at least 10000 samples */
 	/* The number of samples has a large effect on index build time */
@@ -473,7 +510,7 @@ CreateListPages(Relation index, VectorArray centers, int dimensions,
 	IvfflatList list;
 
 	listSize = MAXALIGN(IVFFLAT_LIST_SIZE(dimensions));
-	list = palloc0(listSize);
+	list = palloc(listSize);
 
 	buf = IvfflatNewBuffer(index, forkNum);
 	IvfflatInitRegisterPage(index, &buf, &page, &state);
@@ -594,7 +631,11 @@ IvfflatParallelScanAndSort(IvfflatSpool * ivfspool, IvfflatShared * ivfshared, S
 {
 	SortCoordinate coordinate;
 	IvfflatBuildState buildstate;
+#if PG_VERSION_NUM >= 120000
 	TableScanDesc scan;
+#else
+	HeapScanDesc scan;
+#endif
 	double		reltuples;
 	IndexInfo  *indexInfo;
 
@@ -618,11 +659,18 @@ IvfflatParallelScanAndSort(IvfflatSpool * ivfspool, IvfflatShared * ivfshared, S
 	buildstate.centers->length = buildstate.centers->maxlen;
 	ivfspool->sortstate = tuplesort_begin_heap(buildstate.tupdesc, 1, attNums, sortOperators, sortCollations, nullsFirstFlags, sortmem, coordinate, false);
 	buildstate.sortstate = ivfspool->sortstate;
+#if PG_VERSION_NUM >= 120000
 	scan = table_beginscan_parallel(ivfspool->heap,
 									ParallelTableScanFromIvfflatShared(ivfshared));
 	reltuples = table_index_build_scan(ivfspool->heap, ivfspool->index, indexInfo,
 									   true, progress, BuildCallback,
 									   (void *) &buildstate, scan);
+#else
+	scan = heap_beginscan_parallel(ivfspool->heap, &ivfshared->heapdesc);
+	reltuples = IndexBuildHeapScan(ivfspool->heap, ivfspool->index, indexInfo,
+								   true, BuildCallback,
+								   (void *) &buildstate, scan);
+#endif
 
 	/* Execute this worker's part of the sort */
 	tuplesort_performsort(ivfspool->sortstate);
@@ -692,7 +740,11 @@ IvfflatParallelBuildMain(dsm_segment *seg, shm_toc *toc)
 	}
 
 	/* Open relations within worker */
+#if PG_VERSION_NUM >= 120000
 	heapRel = table_open(ivfshared->heaprelid, heapLockmode);
+#else
+	heapRel = heap_open(ivfshared->heaprelid, heapLockmode);
+#endif
 	indexRel = index_open(ivfshared->indexrelid, indexLockmode);
 
 	/* Initialize worker's own spool */
@@ -712,7 +764,11 @@ IvfflatParallelBuildMain(dsm_segment *seg, shm_toc *toc)
 
 	/* Close relations within worker */
 	index_close(indexRel, indexLockmode);
+#if PG_VERSION_NUM >= 120000
 	table_close(heapRel, heapLockmode);
+#else
+	heap_close(heapRel, heapLockmode);
+#endif
 }
 
 /*
@@ -737,7 +793,19 @@ IvfflatEndParallel(IvfflatLeader * ivfleader)
 static Size
 ParallelEstimateShared(Relation heap, Snapshot snapshot)
 {
+#if PG_VERSION_NUM >= 120000
 	return add_size(BUFFERALIGN(sizeof(IvfflatShared)), table_parallelscan_estimate(heap, snapshot));
+#else
+	if (!IsMVCCSnapshot(snapshot))
+	{
+		Assert(snapshot == SnapshotAny);
+		return sizeof(IvfflatShared);
+	}
+
+	return add_size(offsetof(IvfflatShared, heapdesc) +
+					offsetof(ParallelHeapScanDescData, phs_snapshot_data),
+					EstimateSnapshotSpace(snapshot));
+#endif
 }
 
 /*
@@ -788,7 +856,11 @@ IvfflatBeginParallel(IvfflatBuildState * buildstate, bool isconcurrent, int requ
 	/* Enter parallel mode and create context */
 	EnterParallelMode();
 	Assert(request > 0);
+#if PG_VERSION_NUM >= 120000
 	pcxt = CreateParallelContext("vector", "IvfflatParallelBuildMain", request);
+#else
+	pcxt = CreateParallelContext("vector", "IvfflatParallelBuildMain", request, true);
+#endif
 
 	scantuplesortstates = leaderparticipates ? request + 1 : request;
 
@@ -846,9 +918,13 @@ IvfflatBeginParallel(IvfflatBuildState * buildstate, bool isconcurrent, int requ
 #ifdef IVFFLAT_KMEANS_DEBUG
 	ivfshared->inertia = 0;
 #endif
+#if PG_VERSION_NUM >= 120000
 	table_parallelscan_initialize(buildstate->heap,
 								  ParallelTableScanFromIvfflatShared(ivfshared),
 								  snapshot);
+#else
+	heap_parallelscan_initialize(&ivfshared->heapdesc, buildstate->heap, snapshot);
+#endif
 
 	/* Store shared tuplesort-private state, for which we reserved space */
 	sharedsort = (Sharedsort *) shm_toc_allocate(pcxt->toc, estsort);
@@ -919,7 +995,7 @@ AssignTuples(IvfflatBuildState * buildstate)
 	Oid			sortCollations[] = {InvalidOid};
 	bool		nullsFirstFlags[] = {false};
 
-	pgstat_progress_update_param(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_ASSIGN);
+	UpdateProgress(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_ASSIGN);
 
 	/* Calculate parallel workers */
 	if (buildstate->heap != NULL)
@@ -947,8 +1023,15 @@ AssignTuples(IvfflatBuildState * buildstate)
 		if (buildstate->ivfleader)
 			buildstate->reltuples = ParallelHeapScan(buildstate);
 		else
+		{
+#if PG_VERSION_NUM >= 120000
 			buildstate->reltuples = table_index_build_scan(buildstate->heap, buildstate->index, buildstate->indexInfo,
 														   true, true, BuildCallback, (void *) buildstate, NULL);
+#else
+			buildstate->reltuples = IndexBuildHeapScan(buildstate->heap, buildstate->index, buildstate->indexInfo,
+													   true, BuildCallback, (void *) buildstate, NULL);
+#endif
+		}
 
 #ifdef IVFFLAT_KMEANS_DEBUG
 		PrintKmeansMetrics(buildstate);

src/ivfflat.c

@@ -3,16 +3,14 @@
 #include <float.h>
 
 #include "access/amapi.h"
-#include "access/reloptions.h"
-#include "commands/progress.h"
 #include "commands/vacuum.h"
 #include "ivfflat.h"
 #include "utils/guc.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
 
-#if PG_VERSION_NUM < 150000
+#if PG_VERSION_NUM >= 120000
-#define MarkGUCPrefixReserved(x) EmitWarningsOnPlaceholders(x)
+#include "commands/progress.h"
 #endif
 
 int			ivfflat_probes;
@@ -35,13 +33,12 @@ IvfflatInit(void)
 	DefineCustomIntVariable("ivfflat.probes", "Sets the number of probes",
 							"Valid range is 1..lists.", &ivfflat_probes,
 							IVFFLAT_DEFAULT_PROBES, IVFFLAT_MIN_LISTS, IVFFLAT_MAX_LISTS, PGC_USERSET, 0, NULL, NULL, NULL);
-
-	MarkGUCPrefixReserved("ivfflat");
 }
 
 /*
  * Get the name of index build phase
  */
+#if PG_VERSION_NUM >= 120000
 static char *
 ivfflatbuildphasename(int64 phasenum)
 {
@@ -59,6 +56,7 @@ ivfflatbuildphasename(int64 phasenum)
 			return NULL;
 	}
 }
+#endif
 
 /*
  * Estimate the cost of an index scan
@@ -74,6 +72,9 @@ ivfflatcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
 	double		ratio;
 	double		spc_seq_page_cost;
 	Relation	index;
+#if PG_VERSION_NUM < 120000
+	List	   *qinfos;
+#endif
 
 	/* Never use index without order */
 	if (path->indexorderbys == NULL)
@@ -104,7 +105,26 @@ ivfflatcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
 	 */
 	costs.numIndexTuples = path->indexinfo->tuples * ratio;
 
+	/*
+	 * Do not use index if no limit or limit + offset > expected tuples unless
+	 * enable_seqscan = off
+	 */
+	if (root->limit_tuples < 0 || root->limit_tuples > costs.numIndexTuples)
+	{
+		*indexStartupCost = 1.0e10 - 1;
+		*indexTotalCost = 1.0e10 - 1;
+		*indexSelectivity = 0;
+		*indexCorrelation = 0;
+		*indexPages = 0;
+		return;
+	}
+
+#if PG_VERSION_NUM >= 120000
 	genericcostestimate(root, path, loop_count, &costs);
+#else
+	qinfos = deconstruct_indexquals(path);
+	genericcostestimate(root, path, loop_count, qinfos, &costs);
+#endif
 
 	get_tablespace_page_costs(path->indexinfo->reltablespace, NULL, &spc_seq_page_cost);
 
@@ -221,7 +241,9 @@ ivfflathandler(PG_FUNCTION_ARGS)
 	amroutine->amcostestimate = ivfflatcostestimate;
 	amroutine->amoptions = ivfflatoptions;
 	amroutine->amproperty = NULL;	/* TODO AMPROP_DISTANCE_ORDERABLE */
+#if PG_VERSION_NUM >= 120000
 	amroutine->ambuildphasename = ivfflatbuildphasename;
+#endif
 	amroutine->amvalidate = ivfflatvalidate;
 #if PG_VERSION_NUM >= 140000
 	amroutine->amadjustmembers = NULL;

src/ivfflat.h

@@ -3,10 +3,9 @@
 
 #include "postgres.h"
 
-#include "access/genam.h"
 #include "access/generic_xlog.h"
 #include "access/parallel.h"
-#include "lib/pairingheap.h"
+#include "access/reloptions.h"
 #include "nodes/execnodes.h"
 #include "port.h"				/* for random() */
 #include "utils/sampling.h"
@@ -17,6 +16,10 @@
 #include "common/pg_prng.h"
 #endif
 
+#if PG_VERSION_NUM < 120000
+#include "access/relscan.h"
+#endif
+
 #ifdef IVFFLAT_BENCH
 #include "portability/instr_time.h"
 #endif
@@ -132,10 +135,16 @@ typedef struct IvfflatShared
 #ifdef IVFFLAT_KMEANS_DEBUG
 	double		inertia;
 #endif
+
+#if PG_VERSION_NUM < 120000
+	ParallelHeapScanDescData heapdesc;	/* must come last */
+#endif
 }			IvfflatShared;
 
+#if PG_VERSION_NUM >= 120000
 #define ParallelTableScanFromIvfflatShared(shared) \
 	(ParallelTableScanDesc) ((char *) (shared) + BUFFERALIGN(sizeof(IvfflatShared)))
+#endif
 
 typedef struct IvfflatLeader
 {

src/ivfinsert.c

@@ -2,7 +2,6 @@
 
 #include <float.h>
 
-#include "access/generic_xlog.h"
 #include "ivfflat.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"

src/ivfscan.c

@@ -5,7 +5,6 @@
 #include "access/relscan.h"
 #include "catalog/pg_operator_d.h"
 #include "catalog/pg_type_d.h"
-#include "lib/pairingheap.h"
 #include "ivfflat.h"
 #include "miscadmin.h"
 #include "pgstat.h"
@@ -106,7 +105,12 @@ GetScanItems(IndexScanDesc scan, Datum value)
 	IvfflatScanOpaque so = (IvfflatScanOpaque) scan->opaque;
 	TupleDesc	tupdesc = RelationGetDescr(scan->indexRelation);
 	double		tuples = 0;
+
+#if PG_VERSION_NUM >= 120000
 	TupleTableSlot *slot = MakeSingleTupleTableSlot(so->tupdesc, &TTSOpsVirtual);
+#else
+	TupleTableSlot *slot = MakeSingleTupleTableSlot(so->tupdesc);
+#endif
 
 	/*
 	 * Reuse same set of shared buffers for scan
@@ -212,14 +216,22 @@ ivfflatbeginscan(Relation index, int nkeys, int norderbys)
 	so->collation = index->rd_indcollation[0];
 
 	/* Create tuple description for sorting */
+#if PG_VERSION_NUM >= 120000
 	so->tupdesc = CreateTemplateTupleDesc(2);
+#else
+	so->tupdesc = CreateTemplateTupleDesc(2, false);
+#endif
 	TupleDescInitEntry(so->tupdesc, (AttrNumber) 1, "distance", FLOAT8OID, -1, 0);
 	TupleDescInitEntry(so->tupdesc, (AttrNumber) 2, "heaptid", TIDOID, -1, 0);
 
 	/* Prep sort */
 	so->sortstate = tuplesort_begin_heap(so->tupdesc, 1, attNums, sortOperators, sortCollations, nullsFirstFlags, work_mem, NULL, false);
 
+#if PG_VERSION_NUM >= 120000
 	so->slot = MakeSingleTupleTableSlot(so->tupdesc, &TTSOpsMinimalTuple);
+#else
+	so->slot = MakeSingleTupleTableSlot(so->tupdesc);
+#endif
 
 	so->listQueue = pairingheap_allocate(CompareLists, scan);
 
@@ -309,8 +321,12 @@ ivfflatgettuple(IndexScanDesc scan, ScanDirection dir)
 	{
 		ItemPointer heaptid = (ItemPointer) DatumGetPointer(slot_getattr(so->slot, 2, &so->isnull));
 
+#if PG_VERSION_NUM >= 120000
 		scan->xs_heaptid = *heaptid;
-		scan->xs_recheck = false;
+#else
+		scan->xs_ctup.t_self = *heaptid;
+#endif
+
 		scan->xs_recheckorderby = false;
 		return true;
 	}

src/ivfutils.c

@@ -1,6 +1,5 @@
 #include "postgres.h"
 
-#include "access/generic_xlog.h"
 #include "ivfflat.h"
 #include "storage/bufmgr.h"
 #include "vector.h"

src/ivfvacuum.c

@@ -1,6 +1,5 @@
 #include "postgres.h"
 
-#include "access/generic_xlog.h"
 #include "commands/vacuum.h"
 #include "ivfflat.h"
 #include "storage/bufmgr.h"

src/vector.c

@@ -3,7 +3,6 @@
 #include <math.h>
 
 #include "catalog/pg_type.h"
-#include "common/shortest_dec.h"
 #include "fmgr.h"
 #include "hnsw.h"
 #include "ivfflat.h"
@@ -12,7 +11,6 @@
 #include "port.h"				/* for strtof() */
 #include "utils/array.h"
 #include "utils/builtins.h"
-#include "utils/float.h"
 #include "utils/lsyscache.h"
 #include "utils/numeric.h"
 #include "vector.h"
@@ -21,6 +19,13 @@
 #include "varatt.h"
 #endif
 
+#if PG_VERSION_NUM >= 120000
+#include "common/shortest_dec.h"
+#include "utils/float.h"
+#else
+#include <float.h>
+#endif
+
 #if PG_VERSION_NUM < 130000
 #define TYPALIGN_DOUBLE 'd'
 #define TYPALIGN_INT 'i'
@@ -288,6 +293,15 @@ vector_out(PG_FUNCTION_ARGS)
 	char	   *ptr;
 	int			n;
 
+#if PG_VERSION_NUM < 120000
+	int			ndig = FLT_DIG + extra_float_digits;
+
+	if (ndig < 1)
+		ndig = 1;
+
+#define FLOAT_SHORTEST_DECIMAL_LEN (ndig + 10)
+#endif
+
 	/*
 	 * Need:
 	 *
@@ -311,7 +325,11 @@ vector_out(PG_FUNCTION_ARGS)
 			ptr++;
 		}
 
+#if PG_VERSION_NUM >= 120000
 		n = float_to_shortest_decimal_bufn(vector->x[i], ptr);
+#else
+		n = sprintf(ptr, "%.*g", ndig, vector->x[i]);
+#endif
 		ptr += n;
 	}
 	*ptr = ']';

test/t/012_hnsw_build_recall.pl

@@ -95,10 +95,11 @@ for my $i (0 .. $#operators)
 
 	$node->safe_psql("postgres", "DROP INDEX idx;");
 
-	# Build index in parallel in memory
+	# Build index in parallel
 	my ($ret, $stdout, $stderr) = $node->psql("postgres", qq(
 		SET client_min_messages = DEBUG;
 		SET min_parallel_table_scan_size = 1;
+		SET hnsw.enable_parallel_build = on;
 		CREATE INDEX idx ON tst USING hnsw (v $opclass);
 	));
 	is($ret, 0, $stderr);
@@ -108,21 +109,6 @@ for my $i (0 .. $#operators)
 	test_recall($min, $operator);
 
 	$node->safe_psql("postgres", "DROP INDEX idx;");
-
-	# Build index in parallel on disk
-	# Set parallel_workers on table to use workers with low maintenance_work_mem
-	($ret, $stdout, $stderr) = $node->psql("postgres", qq(
-		ALTER TABLE tst SET (parallel_workers = 2);
-		SET client_min_messages = DEBUG;
-		SET maintenance_work_mem = '4MB';
-		CREATE INDEX idx ON tst USING hnsw (v $opclass);
-		ALTER TABLE tst RESET (parallel_workers);
-	));
-	is($ret, 0, $stderr);
-	like($stderr, qr/using \d+ parallel workers/);
-	like($stderr, qr/hnsw graph no longer fits into maintenance_work_mem/);
-
-	$node->safe_psql("postgres", "DROP INDEX idx;");
 }
 
 done_testing();

test/t/018_hnsw_filtering.pl

@@ -1,114 +0,0 @@
-use strict;
-use warnings;
-use PostgresNode;
-use TestLib;
-use Test::More;
-
-my $dim = 3;
-my $nc = 50;
-my $limit = 20;
-
-my $array_sql = join(",", ('random()') x $dim);
-
-# Initialize node
-my $node = get_new_node('node');
-$node->init;
-$node->start;
-
-# Create table and index
-$node->safe_psql("postgres", "CREATE EXTENSION vector;");
-$node->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector($dim), c int4, t text);");
-$node->safe_psql("postgres",
-	"INSERT INTO tst SELECT i, ARRAY[$array_sql], i % $nc, 'test ' || i FROM generate_series(1, 10000) i;"
-);
-$node->safe_psql("postgres", "CREATE INDEX idx ON tst USING hnsw (v vector_l2_ops);");
-$node->safe_psql("postgres", "ANALYZE tst;");
-
-# Generate query
-my @r = ();
-for (1 .. $dim)
-{
-	push(@r, rand());
-}
-my $query = "[" . join(",", @r) . "]";
-my $c = int(rand() * $nc);
-
-# Test attribute filtering
-my $explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c = $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Do not use index
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with few rows removed
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c != $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with few rows removed comparison
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c >= 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with many rows removed comparison
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c < 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Do not use index
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with few rows removed like
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE t LIKE '%%test%%' ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with many rows removed like
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE t LIKE '%%other%%' ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Seq Scan/);
-
-# Test distance filtering
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' < 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test distance filtering greater than distance
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' > 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Do not use index
-like($explain, qr/Index Scan using idx/);
-
-# Test distance filtering without order
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' < 1;
-));
-like($explain, qr/Seq Scan/);
-
-# Test distance filtering without limit
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' < 1 ORDER BY v <-> '$query';
-));
-like($explain, qr/Seq Scan/);
-
-# Test attribute index
-$node->safe_psql("postgres", "CREATE INDEX attribute_idx ON tst (c);");
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c = $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Use attribute index
-like($explain, qr/Index Scan using idx/);
-
-# Test partial index
-$node->safe_psql("postgres", "CREATE INDEX partial_idx ON tst USING hnsw (v vector_l2_ops) WHERE (c = $c);");
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c = $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using partial_idx/);
-
-done_testing();

test/t/019_ivfflat_filtering.pl

@@ -1,116 +0,0 @@
-use strict;
-use warnings;
-use PostgresNode;
-use TestLib;
-use Test::More;
-
-my $dim = 3;
-my $nc = 50;
-my $limit = 20;
-
-my $array_sql = join(",", ('random()') x $dim);
-
-# Initialize node
-my $node = get_new_node('node');
-$node->init;
-$node->start;
-
-# Create table and index
-$node->safe_psql("postgres", "CREATE EXTENSION vector;");
-$node->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector($dim), c int4, t text);");
-$node->safe_psql("postgres",
-	"INSERT INTO tst SELECT i, ARRAY[$array_sql], i % $nc, 'test ' || i FROM generate_series(1, 10000) i;"
-);
-$node->safe_psql("postgres", "CREATE INDEX idx ON tst USING ivfflat (v vector_l2_ops) WITH (lists = 100);");
-$node->safe_psql("postgres", "ANALYZE tst;");
-
-# Generate query
-my @r = ();
-for (1 .. $dim)
-{
-	push(@r, rand());
-}
-my $query = "[" . join(",", @r) . "]";
-my $c = int(rand() * $nc);
-
-# Test attribute filtering
-my $explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c = $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Do not use index
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with few rows removed
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c != $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with few rows removed comparison
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c >= 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with many rows removed comparison
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c < 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Do not use index
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with few rows removed like
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE t LIKE '%%test%%' ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute filtering with many rows removed like
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE t LIKE '%%other%%' ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Seq Scan/);
-
-# Test distance filtering
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' < 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-like($explain, qr/Index Scan using idx/);
-
-# Test distance filtering greater than distance
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' > 1 ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Do not use index
-like($explain, qr/Index Scan using idx/);
-
-# Test distance filtering without order
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' < 1;
-));
-like($explain, qr/Seq Scan/);
-
-# Test distance filtering without limit
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE v <-> '$query' < 1 ORDER BY v <-> '$query';
-));
-# TODO Do not use index
-like($explain, qr/Index Scan using idx/);
-
-# Test attribute index
-$node->safe_psql("postgres", "CREATE INDEX attribute_idx ON tst (c);");
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c = $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Use attribute index
-like($explain, qr/Index Scan using idx/);
-
-# Test partial index
-$node->safe_psql("postgres", "CREATE INDEX partial_idx ON tst USING ivfflat (v vector_l2_ops) WITH (lists = 5) WHERE (c = $c);");
-$explain = $node->safe_psql("postgres", qq(
-	EXPLAIN ANALYZE SELECT i FROM tst WHERE c = $c ORDER BY v <-> '$query' LIMIT $limit;
-));
-# TODO Use partial index
-like($explain, qr/Index Scan using idx/);
-
-done_testing();

test/t/019_ivfflat_limit.pl

@@ -0,0 +1,64 @@
+use strict;
+use warnings;
+use PostgresNode;
+use TestLib;
+use Test::More;
+
+# Initialize node
+my $node = get_new_node('node');
+$node->init;
+$node->start;
+
+# Create table and index
+$node->safe_psql("postgres", "CREATE EXTENSION vector;");
+$node->safe_psql("postgres", "CREATE TABLE tst (v vector(3));");
+$node->safe_psql("postgres",
+	"INSERT INTO tst SELECT ARRAY[random(), random(), random()] FROM generate_series(1, 1000) i;"
+);
+$node->safe_psql("postgres", "CREATE INDEX ON tst USING ivfflat (v vector_l2_ops) WITH (lists = 10);");
+
+# Test limit
+my $explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 100;
+));
+like($explain, qr/Index Scan/);
+
+# Test limit with probes
+$explain = $node->safe_psql("postgres", qq(
+	SET ivfflat.probes = 2;
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 200;
+));
+like($explain, qr/Index Scan/);
+
+# Test limit + offset
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 90 OFFSET 10;
+));
+like($explain, qr/Index Scan/);
+
+# Test limit > expected tuples
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 101;
+));
+like($explain, qr/Seq Scan/);
+
+# Test limit > expected tuples with probes
+$explain = $node->safe_psql("postgres", qq(
+	SET ivfflat.probes = 2;
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 201;
+));
+like($explain, qr/Seq Scan/);
+
+# Test limit + offset > expected tuples
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 91 OFFSET 10;
+));
+like($explain, qr/Seq Scan/);
+
+# Test no limit
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]';
+));
+like($explain, qr/Seq Scan/);
+
+done_testing();

test/t/020_hnsw_limit.pl

@@ -0,0 +1,62 @@
+use strict;
+use warnings;
+use PostgresNode;
+use TestLib;
+use Test::More;
+
+# Initialize node
+my $node = get_new_node('node');
+$node->init;
+$node->start;
+
+# Create table and index
+$node->safe_psql("postgres", "CREATE EXTENSION vector;");
+$node->safe_psql("postgres", "CREATE TABLE tst (v vector(3));");
+$node->safe_psql("postgres",
+	"INSERT INTO tst SELECT ARRAY[random(), random(), random()] FROM generate_series(1, 1000) i;"
+);
+$node->safe_psql("postgres", "CREATE INDEX ON tst USING hnsw (v vector_l2_ops);");
+
+# Test limit
+my $explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 40;
+));
+like($explain, qr/Index Scan/);
+
+# Test limit with CTE
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE WITH cte AS (SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 40) SELECT * FROM cte;
+));
+like($explain, qr/Index Scan/);
+
+# Test limit + offset
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 30 OFFSET 10;
+));
+like($explain, qr/Index Scan/);
+
+# Test limit > ef_search
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 41;
+));
+like($explain, qr/Seq Scan/);
+
+# Test limit > ef_search with CTE
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE WITH cte AS (SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 41) SELECT * FROM cte;
+));
+like($explain, qr/Seq Scan/);
+
+# Test limit + offset > ef_search
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]' LIMIT 31 OFFSET 10;
+));
+like($explain, qr/Seq Scan/);
+
+# Test no limit
+$explain = $node->safe_psql("postgres", qq(
+	EXPLAIN ANALYZE SELECT * FROM tst ORDER BY v <-> '[1,2,3]';
+));
+like($explain, qr/Seq Scan/);
+
+done_testing();

vector.control

@@ -1,4 +1,4 @@
 comment = 'vector data type and ivfflat and hnsw access methods'
-default_version = '0.6.0'
+default_version = '0.5.1'
 module_pathname = '$libdir/vector'
 relocatable = true