Added bound option

.editorconfig

@@ -1,6 +1,6 @@
 root = true
 
-[*.{c,h}]
+[*.{c,h,pl}]
 indent_style = tab
 indent_size = tab
 tab_width = 4

CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.2.5 (2022-02-11)
+
+- Reduced memory usage during index creation
+- Fixed index creation exceeding `maintenance_work_mem`
+- Fixed error with index creation when lists > 1600
+
 ## 0.2.4 (2022-02-06)
 
 - Added support for parallel vacuum

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": "0.2.4",
+	"version": "0.2.5",
 	"maintainer": [
 		"Andrew Kane <andrew@ankane.org>"
 	],
@@ -20,7 +20,7 @@
 		"vector": {
 			"file": "sql/vector.sql",
 			"docfile": "README.md",
-			"version": "0.2.4",
+			"version": "0.2.5",
 			"abstract": "Open-source vector similarity search for Postgres"
 		}
 	},

Makefile

@@ -1,5 +1,5 @@
 EXTENSION = vector
-EXTVERSION = 0.2.4
+EXTVERSION = 0.2.5
 
 MODULE_big = vector
 DATA = $(wildcard sql/*--*.sql)
@@ -21,7 +21,7 @@ endif
 # For auto-vectorization:
 # - GCC (needs -ftree-vectorize OR -O3) - https://gcc.gnu.org/projects/tree-ssa/vectorization.html
 # - Clang (could use pragma instead) - https://llvm.org/docs/Vectorizers.html
-PG_CFLAGS = $(OPTFLAGS) -ftree-vectorize -fassociative-math -fno-signed-zeros -fno-trapping-math
+PG_CFLAGS += $(OPTFLAGS) -ftree-vectorize -fassociative-math -fno-signed-zeros -fno-trapping-math
 
 # Debug GCC auto-vectorization
 # PG_CFLAGS += -fopt-info-vec

README.md

@@ -17,7 +17,7 @@ Supports L2 distance, inner product, and cosine distance
 Compile and install the extension (supports Postgres 9.6+)
 
 ```sh
-git clone --branch v0.2.4 https://github.com/pgvector/pgvector.git
+git clone --branch v0.2.5 https://github.com/pgvector/pgvector.git
 cd pgvector
 make
 make install # may need sudo
@@ -77,19 +77,7 @@ Cosine distance
 CREATE INDEX ON table USING ivfflat (column vector_cosine_ops);
 ```
 
-Indexes should be created after the table has data for optimal clustering. If the distribution of data changes significantly, you can reindex without downtime:
+Indexes should be created after the table has some data for optimal clustering. Also, unlike typical indexes which only affect performance, you may see different results for queries after adding an approximate index.
-
-```sql
--- Postgres 12+
-REINDEX INDEX CONCURRENTLY index_name;
-
--- Postgres < 12
-CREATE INDEX CONCURRENTLY temp_name ON table USING ivfflat (column opclass);
-DROP INDEX CONCURRENTLY index_name;
-ALTER INDEX temp_name RENAME TO index_name;
-```
-
-Also, unlike typical indexes which only affect performance, you may see different results for queries after adding an approximate index.
 
 ### Index Options
 
@@ -194,6 +182,7 @@ Libraries that use pgvector:
 
 - [pgvector-python](https://github.com/pgvector/pgvector-python) (Python)
 - [Neighbor](https://github.com/ankane/neighbor) (Ruby)
+- [pgvector-ruby](https://github.com/pgvector/pgvector-ruby) (Ruby)
 - [pgvector-node](https://github.com/pgvector/pgvector-node) (Node.js)
 - [pgvector-go](https://github.com/pgvector/pgvector-go) (Go)
 - [pgvector-rust](https://github.com/pgvector/pgvector-rust) (Rust)
@@ -231,7 +220,7 @@ This adds pgvector to the [Postgres image](https://hub.docker.com/_/postgres).
 You can also build the image manually
 
 ```sh
-git clone --branch v0.2.4 https://github.com/pgvector/pgvector.git
+git clone --branch v0.2.5 https://github.com/pgvector/pgvector.git
 cd pgvector
 docker build -t pgvector .
 ```
@@ -315,6 +304,12 @@ make installcheck REGRESS=functions                    # regression test
 make prove_installcheck PROVE_TESTS=test/t/001_wal.pl  # TAP test
 ```
 
+To enable benchmarking:
+
+```sh
+make clean && PG_CFLAGS=-DIVFFLAT_BENCH make && make install
+```
+
 Resources for contributors
 
 - [Extension Building Infrastructure](https://www.postgresql.org/docs/current/extend-pgxs.html)

sql/vector--0.2.4--0.2.5.sql

@@ -0,0 +1,2 @@
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "ALTER EXTENSION vector UPDATE TO '0.2.5'" to load this file. \quit

src/ivfbuild.c

@@ -36,16 +36,11 @@
 #define CALLBACK_ITEM_POINTER HeapTuple hup
 #endif
 
-/*
- * Update build phase progress
- */
-static inline void
-UpdateProgress(int index, int64 val)
-{
 #if PG_VERSION_NUM >= 120000
-	pgstat_progress_update_param(index, val);
+#define UpdateProgress(index, val) pgstat_progress_update_param(index, val)
+#else
+#define UpdateProgress(index, val) ((void)val)
 #endif
-}
 
 /*
  * Callback for sampling
@@ -170,6 +165,10 @@ BuildCallback(Relation index, CALLBACK_ITEM_POINTER, Datum *values,
 		}
 	}
 
+#ifdef IVFFLAT_KMEANS_DEBUG
+	buildstate->inertia += minDistance;
+#endif
+
 	/* Create a virtual tuple */
 	ExecClearTuple(slot);
 	slot->tts_values[0] = Int32GetDatum(closestCenter);
@@ -350,6 +349,10 @@ InitBuildState(IvfflatBuildState * buildstate, Relation heap, Relation index, In
 
 	/* Reuse for each tuple */
 	buildstate->normvec = InitVector(buildstate->dimensions);
+
+#ifdef IVFFLAT_KMEANS_DEBUG
+	buildstate->inertia = 0;
+#endif
 }
 
 /*
@@ -377,14 +380,19 @@ ComputeCenters(IvfflatBuildState * buildstate)
 	if (numSamples < 10000)
 		numSamples = 10000;
 
-	/* Sample samples */
+	/* Skip samples for unlogged table */
+	if (buildstate->heap == NULL)
+		numSamples = 1;
+
+	/* Sample rows */
+	/* TODO Ensure within maintenance_work_mem */
 	buildstate->samples = VectorArrayInit(numSamples, buildstate->dimensions);
 	if (buildstate->heap != NULL)
 		SampleRows(buildstate);
 
 	/* Calculate centers */
 	UpdateProgress(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_KMEANS);
-	IvfflatKmeans(buildstate->index, buildstate->samples, buildstate->centers);
+	IvfflatBench("k-means", IvfflatKmeans(buildstate->index, buildstate->samples, buildstate->centers));
 
 	/* Free samples before we allocate more memory */
 	pfree(buildstate->samples);
@@ -497,8 +505,14 @@ CreateEntryPages(IvfflatBuildState * buildstate, ForkNumber forkNum)
 #endif
 	}
 
-	/* Sort and insert */
+	/* Sort */
 	tuplesort_performsort(buildstate->sortstate);
+
+#ifdef IVFFLAT_KMEANS_DEBUG
+	elog(INFO, "inertia: %.3e", buildstate->inertia);
+#endif
+
+	/* Insert */
 	InsertTuples(buildstate->index, buildstate, forkNum);
 	tuplesort_end(buildstate->sortstate);
 }
@@ -517,7 +531,7 @@ BuildIndex(Relation heap, Relation index, IndexInfo *indexInfo,
 	/* Create pages */
 	CreateMetaPage(index, buildstate->dimensions, buildstate->lists, forkNum);
 	CreateListPages(index, buildstate->centers, buildstate->dimensions, buildstate->lists, forkNum, &buildstate->listInfo);
-	CreateEntryPages(buildstate, forkNum);
+	IvfflatBench("CreateEntryPages", CreateEntryPages(buildstate, forkNum));
 
 	FreeBuildState(buildstate);
 }

src/ivfflat.c

@@ -13,6 +13,7 @@
 #endif
 
 int			ivfflat_probes;
+int			ivfflat_bound;
 static relopt_kind ivfflat_relopt_kind;
 
 /*
@@ -32,6 +33,10 @@ _PG_init(void)
 	DefineCustomIntVariable("ivfflat.probes", "Sets the number of probes",
 							"Valid range is 1..lists.", &ivfflat_probes,
 							1, 1, IVFFLAT_MAX_LISTS, PGC_USERSET, 0, NULL, NULL, NULL);
+
+	DefineCustomIntVariable("ivfflat.bound", "Sets the max results from index (experimental)",
+							NULL, &ivfflat_bound,
+							0, 0, INT_MAX, PGC_USERSET, 0, NULL, NULL, NULL);
 }
 
 /*
@@ -159,6 +164,11 @@ ivfflatvalidate(Oid opclassoid)
 	return true;
 }
 
+/*
+ * Define index handler
+ *
+ * See https://www.postgresql.org/docs/current/index-api.html
+ */
 PG_FUNCTION_INFO_V1(ivfflathandler);
 Datum
 ivfflathandler(PG_FUNCTION_ARGS)
@@ -193,6 +203,7 @@ ivfflathandler(PG_FUNCTION_ARGS)
 #endif
 	amroutine->amkeytype = InvalidOid;
 
+	/* Interface functions */
 	amroutine->ambuild = ivfflatbuild;
 	amroutine->ambuildempty = ivfflatbuildempty;
 	amroutine->aminsert = ivfflatinsert;
@@ -206,6 +217,9 @@ ivfflathandler(PG_FUNCTION_ARGS)
 	amroutine->ambuildphasename = ivfflatbuildphasename;
 #endif
 	amroutine->amvalidate = ivfflatvalidate;
+#if PG_VERSION_NUM >= 140000
+	amroutine->amadjustmembers = NULL;
+#endif
 	amroutine->ambeginscan = ivfflatbeginscan;
 	amroutine->amrescan = ivfflatrescan;
 	amroutine->amgettuple = ivfflatgettuple;
@@ -213,6 +227,8 @@ ivfflathandler(PG_FUNCTION_ARGS)
 	amroutine->amendscan = ivfflatendscan;
 	amroutine->ammarkpos = NULL;
 	amroutine->amrestrpos = NULL;
+
+	/* Interface functions to support parallel index scans */
 #if PG_VERSION_NUM >= 100000
 	amroutine->amestimateparallelscan = NULL;
 	amroutine->aminitparallelscan = NULL;

src/ivfflat.h

@@ -10,6 +10,14 @@
 #include "utils/tuplesort.h"
 #include "vector.h"
 
+#ifdef IVFFLAT_BENCH
+#include "portability/instr_time.h"
+#endif
+
+#if PG_VERSION_NUM < 90600
+#error "Requires PostgreSQL 9.6+"
+#endif
+
 /* Support functions */
 #define IVFFLAT_DISTANCE_PROC 1
 #define IVFFLAT_NORM_PROC 2
@@ -39,6 +47,21 @@
 #define IvfflatPageGetOpaque(page)	((IvfflatPageOpaque) PageGetSpecialPointer(page))
 #define IvfflatPageGetMeta(page)	((IvfflatMetaPageData *) PageGetContents(page))
 
+#ifdef IVFFLAT_BENCH
+#define IvfflatBench(name, code) \
+	do { \
+		instr_time	start; \
+		instr_time	duration; \
+		INSTR_TIME_SET_CURRENT(start); \
+		(code); \
+		INSTR_TIME_SET_CURRENT(duration); \
+		INSTR_TIME_SUBTRACT(duration, start); \
+		elog(INFO, "%s: %.3f ms", name, INSTR_TIME_GET_MILLISEC(duration)); \
+	} while (0)
+#else
+#define IvfflatBench(name, code) (code)
+#endif
+
 #if PG_VERSION_NUM < 100000
 #define ItemPointerGetBlockNumberNoCheck ItemPointerGetBlockNumber
 #define ItemPointerGetOffsetNumberNoCheck ItemPointerGetOffsetNumber
@@ -46,6 +69,7 @@
 
 /* Variables */
 extern int	ivfflat_probes;
+extern int	ivfflat_bound;
 
 typedef struct VectorArrayData
 {
@@ -97,6 +121,10 @@ typedef struct IvfflatBuildState
 	ListInfo   *listInfo;
 	Vector	   *normvec;
 
+#ifdef IVFFLAT_KMEANS_DEBUG
+	double		inertia;
+#endif
+
 	/* Sampling */
 	BlockSamplerData bs;
 	ReservoirStateData rstate;

src/ivfkmeans.c

@@ -11,7 +11,7 @@
  * https://theory.stanford.edu/~sergei/papers/kMeansPP-soda.pdf
  */
 static void
-InitCenters(Relation index, VectorArray samples, VectorArray centers, double *lowerBound)
+InitCenters(Relation index, VectorArray samples, VectorArray centers, float *lowerBound)
 {
 	FmgrInfo   *procinfo;
 	Oid			collation;
@@ -21,7 +21,7 @@ InitCenters(Relation index, VectorArray samples, VectorArray centers, double *lo
 	double		sum;
 	double		choice;
 	Vector	   *vec;
-	double	   *weight = palloc(samples->length * sizeof(double));
+	float	   *weight = palloc(samples->length * sizeof(float));
 	int			numCenters = centers->maxlen;
 	int			numSamples = samples->length;
 
@@ -121,15 +121,18 @@ QuickCenters(Relation index, VectorArray samples, VectorArray centers)
 	FmgrInfo   *normprocinfo = IvfflatOptionalProcInfo(index, IVFFLAT_KMEANS_NORM_PROC);
 
 	/* Copy existing vectors while avoiding duplicates */
-	qsort(samples->items, samples->length, VECTOR_SIZE(samples->dim), CompareVectors);
+	if (samples->length > 0)
-	for (i = 0; i < samples->length; i++)
 	{
-		vec = VectorArrayGet(samples, i);
+		qsort(samples->items, samples->length, VECTOR_SIZE(samples->dim), CompareVectors);
-
+		for (i = 0; i < samples->length; i++)
-		if (i == 0 || CompareVectors(vec, VectorArrayGet(samples, i - 1)) != 0)
 		{
-			VectorArraySet(centers, centers->length, vec);
+			vec = VectorArrayGet(samples, i);
-			centers->length++;
+
+			if (i == 0 || CompareVectors(vec, VectorArrayGet(samples, i - 1)) != 0)
+			{
+				VectorArraySet(centers, centers->length, vec);
+				centers->length++;
+			}
 		}
 	}
 
@@ -177,11 +180,11 @@ ElkanKmeans(Relation index, VectorArray samples, VectorArray centers)
 	VectorArray newCenters;
 	int		   *centerCounts;
 	int		   *closestCenters;
-	double	   *lowerBound;
+	float	   *lowerBound;
-	double	   *upperBound;
+	float	   *upperBound;
-	double	   *s;
+	float	   *s;
-	double	   *halfcdist;
+	float	   *halfcdist;
-	double	   *newcdist;
+	float	   *newcdist;
 	int			changes;
 	double		minDistance;
 	int			closestCenter;
@@ -191,19 +194,43 @@ ElkanKmeans(Relation index, VectorArray samples, VectorArray centers)
 	double		dxcx;
 	double		dxc;
 
+	/* Calculate allocation sizes */
+	Size		samplesSize = VECTOR_ARRAY_SIZE(samples->maxlen, samples->dim);
+	Size		centersSize = VECTOR_ARRAY_SIZE(centers->maxlen, centers->dim);
+	Size		newCentersSize = VECTOR_ARRAY_SIZE(numCenters, dimensions);
+	Size		centerCountsSize = sizeof(int) * numCenters;
+	Size		closestCentersSize = sizeof(int) * numSamples;
+	Size		lowerBoundSize = sizeof(float) * numSamples * numCenters;
+	Size		upperBoundSize = sizeof(float) * numSamples;
+	Size		sSize = sizeof(float) * numCenters;
+	Size		halfcdistSize = sizeof(float) * numCenters * numCenters;
+	Size		newcdistSize = sizeof(float) * numCenters;
+
+	/* Calculate total size */
+	Size		totalSize = samplesSize + centersSize + newCentersSize + centerCountsSize + closestCentersSize + lowerBoundSize + upperBoundSize + sSize + halfcdistSize + newcdistSize;
+
+	/* Check memory requirements */
+	/* Add one to error message to ceil */
+	if (totalSize / 1024 > maintenance_work_mem)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("memory required is %zu MB, maintenance_work_mem is %d MB",
+						totalSize / (1024 * 1024) + 1, maintenance_work_mem / 1024)));
+
 	/* Set support functions */
 	procinfo = index_getprocinfo(index, 1, IVFFLAT_KMEANS_DISTANCE_PROC);
 	normprocinfo = IvfflatOptionalProcInfo(index, IVFFLAT_KMEANS_NORM_PROC);
 	collation = index->rd_indcollation[0];
 
 	/* Allocate space */
-	centerCounts = palloc(sizeof(int) * numCenters);
+	/* Use float instead of double to save memory */
-	closestCenters = palloc(sizeof(int) * numSamples);
+	centerCounts = palloc(centerCountsSize);
-	lowerBound = palloc(sizeof(double) * numSamples * numCenters);
+	closestCenters = palloc(closestCentersSize);
-	upperBound = palloc(sizeof(double) * numSamples);
+	lowerBound = palloc_extended(lowerBoundSize, MCXT_ALLOC_HUGE);
-	s = palloc(sizeof(double) * numCenters);
+	upperBound = palloc(upperBoundSize);
-	halfcdist = palloc(sizeof(double) * numCenters * numCenters);
+	s = palloc(sSize);
-	newcdist = palloc(sizeof(double) * numCenters);
+	halfcdist = palloc(halfcdistSize);
+	newcdist = palloc(newcdistSize);
 
 	newCenters = VectorArrayInit(numCenters, dimensions);
 	for (j = 0; j < numCenters; j++)

src/ivfscan.c

@@ -73,6 +73,7 @@ GetScanLists(IndexScanDesc scan, Datum value)
 	}
 
 	/* Sort by distance */
+	/* TODO Use heap for performance */
 	qsort(so->lists, listCount, sizeof(IvfflatScanList), CompareLists);
 
 	if (so->probes > listCount)
@@ -110,6 +111,10 @@ GetScanItems(IndexScanDesc scan, Datum value)
 	 */
 	BufferAccessStrategy bas = GetAccessStrategy(BAS_BULKREAD);
 
+	/* Set the max number of results */
+	if (ivfflat_bound > 0)
+		tuplesort_set_bound(so->sortstate, ivfflat_bound);
+
 	/* Search closest probes lists */
 	for (i = 0; i < so->probes; i++)
 	{
@@ -153,6 +158,8 @@ GetScanItems(IndexScanDesc scan, Datum value)
 			UnlockReleaseBuffer(buf);
 		}
 	}
+
+	tuplesort_performsort(so->sortstate);
 }
 
 /*
@@ -268,9 +275,8 @@ ivfflatgettuple(IndexScanDesc scan, ScanDirection dir)
 				return false;
 		}
 
-		GetScanLists(scan, value);
+		IvfflatBench("GetScanLists", GetScanLists(scan, value));
-		GetScanItems(scan, value);
+		IvfflatBench("GetScanItems", GetScanItems(scan, value));
-		tuplesort_performsort(so->sortstate);
 		so->first = false;
 
 		/* Clean up if we allocated a new value */

test/expected/input.out

@@ -53,3 +53,12 @@ LINE 1: SELECT '[1,]'::vector;
                ^
 SELECT '[1,2,3]'::vector(2);
 ERROR:  expected 2 dimensions, not 3
+SELECT unnest('{"[1,2,3]", "[4,5,6]"}'::vector[]);
+ unnest  
+---------
+ [1,2,3]
+ [4,5,6]
+(2 rows)
+
+SELECT '{"[1,2,3]"}'::vector(2)[];
+ERROR:  expected 2 dimensions, not 3

test/sql/input.sql

@@ -13,3 +13,6 @@ SELECT '1,2,3'::vector;
 SELECT '[]'::vector;
 SELECT '[1,]'::vector;
 SELECT '[1,2,3]'::vector(2);
+
+SELECT unnest('{"[1,2,3]", "[4,5,6]"}'::vector[]);
+SELECT '{"[1,2,3]"}'::vector(2)[];

test/t/001_wal.pl

@@ -34,9 +34,10 @@ sub test_index_replay
 	my $r2 = rand();
 	my $r3 = rand();
 
-	my $queries = qq(SET enable_seqscan=off;
+	my $queries = qq(
-SELECT * FROM tst ORDER BY v <-> '[$r1,$r2,$r3]' LIMIT 10;
+		SET enable_seqscan = off;
-);
+		SELECT * FROM tst ORDER BY v <-> '[$r1,$r2,$r3]' LIMIT 10;
+	);
 
 	# Run test queries and compare their result
 	my $primary_result = $node_primary->safe_psql("postgres", $queries);
@@ -65,10 +66,9 @@ $node_replica->start;
 $node_primary->safe_psql("postgres", "CREATE EXTENSION vector;");
 $node_primary->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector(3));");
 $node_primary->safe_psql("postgres",
-	"INSERT INTO tst SELECT i%10, ARRAY[random(), random(), random()] FROM generate_series(1,100000) i;"
+	"INSERT INTO tst SELECT i % 10, ARRAY[random(), random(), random()] FROM generate_series(1, 100000) i;"
 );
-$node_primary->safe_psql("postgres",
+$node_primary->safe_psql("postgres", "CREATE INDEX ON tst USING ivfflat (v);");
-	"CREATE INDEX ON tst USING ivfflat (v);");
 
 # Test that queries give same result
 test_index_replay('initial');
@@ -82,7 +82,7 @@ for my $i (1 .. 10)
 	test_index_replay("vacuum $i");
 	my ($start, $end) = (100001 + ($i - 1) * 10000, 100000 + $i * 10000);
 	$node_primary->safe_psql("postgres",
-		"INSERT INTO tst SELECT i%10, ARRAY[random(), random(), random()] FROM generate_series($start,$end) i;"
+		"INSERT INTO tst SELECT i % 10, ARRAY[random(), random(), random()] FROM generate_series($start, $end) i;"
 	);
 	test_index_replay("insert $i");
 }

test/t/002_vacuum.pl

@@ -13,7 +13,7 @@ $node->start;
 $node->safe_psql("postgres", "CREATE EXTENSION vector;");
 $node->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector(3));");
 $node->safe_psql("postgres",
-  "INSERT INTO tst SELECT i%10, ARRAY[i%1000, i%333, i%55] FROM generate_series(1,100000) i;"
+	"INSERT INTO tst SELECT i % 10, ARRAY[i % 1000, i % 333, i % 55] FROM generate_series(1, 100000) i;"
 );
 $node->safe_psql("postgres", "CREATE INDEX ON tst USING ivfflat (v);");
 
@@ -24,7 +24,7 @@ my $size = $node->safe_psql("postgres", "SELECT pg_total_relation_size('tst_v_id
 $node->safe_psql("postgres", "DELETE FROM tst;");
 $node->safe_psql("postgres", "VACUUM tst;");
 $node->safe_psql("postgres",
-  "INSERT INTO tst SELECT i%10, ARRAY[i%1000, i%333, i%55] FROM generate_series(1,100000) i;"
+	"INSERT INTO tst SELECT i % 10, ARRAY[i % 1000, i % 333, i % 55] FROM generate_series(1, 100000) i;"
 );
 
 # Check size

test/t/003_recall.pl

@@ -0,0 +1,72 @@
+use strict;
+use warnings;
+use PostgresNode;
+use TestLib;
+use Test::More tests => 2;
+
+my $node;
+my @queries = ();
+my @expected = ();
+
+sub test_recall
+{
+	my ($probes, $min) = @_;
+	my $correct = 0;
+	my $total = 0;
+
+	for my $i (0 .. $#queries) {
+		my $actual = $node->safe_psql("postgres", qq(
+			SET enable_seqscan = off;
+			SET ivfflat.probes = $probes;
+			SELECT i FROM tst ORDER BY v <-> '$queries[$i]' LIMIT 10;
+		));
+		my @actual_ids = split("\n", $actual);
+		my %actual_set = map { $_ => 1 } @actual_ids;
+
+		my @expected_ids = split("\n", $expected[$i]);
+
+		foreach (@expected_ids) {
+			if (exists($actual_set{$_})) {
+				$correct++;
+			}
+			$total++;
+		}
+	}
+
+	cmp_ok($correct / $total, ">=", $min);
+}
+
+# Initialize node
+$node = get_new_node('node');
+$node->init;
+$node->start;
+
+# Create table
+$node->safe_psql("postgres", "CREATE EXTENSION vector;");
+$node->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector(3));");
+$node->safe_psql("postgres",
+	"INSERT INTO tst SELECT i, ARRAY[random(), random(), random()] FROM generate_series(1, 100000) i;"
+);
+
+# Generate queries
+for (1..20) {
+	my $r1 = rand();
+	my $r2 = rand();
+	my $r3 = rand();
+	push(@queries, "[$r1,$r2,$r3]");
+}
+
+# Get exact results
+foreach (@queries) {
+	my $res = $node->safe_psql("postgres", "SELECT i FROM tst ORDER BY v <-> '$_' LIMIT 10;");
+	push(@expected, $res);
+}
+
+# Add index
+$node->safe_psql("postgres", "CREATE INDEX ON tst USING ivfflat (v);");
+
+# Test approximate results
+test_recall(1, 0.8);
+
+# Test probes
+test_recall(100, 1.0);

test/t/004_centers.pl

@@ -0,0 +1,36 @@
+use strict;
+use warnings;
+use PostgresNode;
+use TestLib;
+use Test::More tests => 3;
+
+# Initialize node
+my $node = get_new_node('node');
+$node->init;
+$node->start;
+
+# Create table
+$node->safe_psql("postgres", "CREATE EXTENSION vector;");
+$node->safe_psql("postgres", "CREATE TABLE tst (i int4, v vector(3));");
+$node->safe_psql("postgres",
+	"INSERT INTO tst SELECT i, '[1,2,3]' FROM generate_series(1, 10) i;"
+);
+
+sub test_centers
+{
+	my ($lists, $min) = @_;
+
+	my ($ret, $stdout, $stderr) = $node->psql("postgres", "CREATE INDEX ON tst USING ivfflat (v) WITH (lists = $lists);");
+	is($ret, 0, $stderr);
+}
+
+# Test no error for duplicate centers
+test_centers(5);
+test_centers(10);
+
+$node->safe_psql("postgres",
+	"INSERT INTO tst SELECT i, '[4,5,6]' FROM generate_series(1, 10) i;"
+);
+
+# Test no error for duplicate centers
+test_centers(10);

vector.control

@@ -1,4 +1,4 @@
 comment = 'vector data type and ivfflat access method'
-default_version = '0.2.4'
+default_version = '0.2.5'
 module_pathname = '$libdir/vector'
 relocatable = true