From d52426b3faa77b26e2693e01cc104df4d766cea8 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Wed, 13 Oct 2021 14:06:55 -0700
Subject: [PATCH] Improved examples [skip ci]

---
 README.md | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index 3241ade..de293dd 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@ Open-source vector similarity search for Postgres
 
 ```sql
 CREATE TABLE table (column vector(3));
-CREATE INDEX ON table USING ivfflat (column);
+CREATE INDEX ON table USING ivfflat (column vector_l2_ops);
 SELECT * FROM table ORDER BY column <-> '[1,2,3]' LIMIT 5;
 ```
 
@@ -62,7 +62,7 @@ Speed up queries with an approximate index. Add an index for each distance funct
 L2 distance
 
 ```sql
-CREATE INDEX ON table USING ivfflat (column vector_l2_ops); -- default if no opclass specified
+CREATE INDEX ON table USING ivfflat (column vector_l2_ops);
 ```
 
 Inner product
@@ -83,8 +83,8 @@ Indexes should be created after the table has data for optimal clustering. If th
 -- Postgres 12+
 REINDEX INDEX CONCURRENTLY index_name;
 
--- Postgres < 12 (change opclass as needed)
-CREATE INDEX CONCURRENTLY temp_name ON table USING ivfflat (column vector_l2_ops);
+-- 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;
 ```
@@ -96,7 +96,7 @@ Also, unlike typical indexes which only affect performance, you may see differen
 Specify the number of inverted lists (100 by default)
 
 ```sql
-CREATE INDEX ON table USING ivfflat (column) WITH (lists = 100);
+CREATE INDEX ON table USING ivfflat (column opclass) WITH (lists = 100);
 ```
 
 ### Query Options
@@ -123,7 +123,7 @@ COMMIT;
 Consider [partial indexes](https://www.postgresql.org/docs/current/indexes-partial.html) for queries with a `WHERE` clause
 
 ```sql
-CREATE INDEX ON table USING ivfflat (column) WHERE (other_column = 123);
+CREATE INDEX ON table USING ivfflat (column opclass) WHERE (other_column = 123);
 ```
 
 To index many different values of `other_column`, consider [partitioning](https://www.postgresql.org/docs/current/ddl-partitioning.html) on `other_column`.
@@ -136,10 +136,10 @@ To speed up queries without an index, increase `max_parallel_workers_per_gather`
 SET max_parallel_workers_per_gather = 4;
 ```
 
-To speed up queries with an index, increase the number of inverted lists.
+To speed up queries with an index, increase the number of inverted lists (at the expense of recall).
 
 ```sql
-CREATE INDEX ON table USING ivfflat (column) WITH (lists = 1000);
+CREATE INDEX ON table USING ivfflat (column opclass) WITH (lists = 1000);
 ```
 
 ## Reference