From 5bc7937715c67add21c8bcc0d4284162c7a0174f Mon Sep 17 00:00:00 2001 From: Andrew Kane Date: Fri, 22 Nov 2024 15:22:06 -0800 Subject: [PATCH] Added iterative index scans to troubleshooting docs [skip ci] --- README.md | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/README.md b/README.md index d103c1f..ef6e9c8 100644 --- a/README.md +++ b/README.md @@ -937,7 +937,7 @@ ALTER TABLE items ALTER COLUMN embedding SET STORAGE PLAIN; #### Why are there less results for a query after adding an HNSW index? -Results are limited by the size of the dynamic candidate list (`hnsw.ef_search`). There may be even less results due to dead tuples or filtering conditions in the query. We recommend setting `hnsw.ef_search` to at least twice the `LIMIT` of the query. If you need more than 500 results, use an IVFFlat index instead. +Results are limited by the size of the dynamic candidate list (`hnsw.ef_search`), which is 40 by default. There may be even less results due to dead tuples or filtering conditions in the query. Enabling [iterative index scans](#iterative-index-scans) can help address this. Also, note that `NULL` vectors are not indexed (as well as zero vectors for cosine distance). @@ -949,7 +949,7 @@ The index was likely created with too little data for the number of lists. Drop DROP INDEX index_name; ``` -Results can also be limited by the number of probes (`ivfflat.probes`). +Results can also be limited by the number of probes (`ivfflat.probes`). Enabling [iterative index scans](#iterative-index-scans) can address this. Also, note that `NULL` vectors are not indexed (as well as zero vectors for cosine distance).