From af052daec5aa282eab2d22fa3b24d6109a30c2f3 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 3 Apr 2019 18:28:18 -0400 Subject: [PATCH] Doc: clarify partial-index example. Jonathan Katz Discussion: https://postgr.es/m/155432280882.722.12392985690846288230@wrigleys.postgresql.org --- doc/src/sgml/indices.sgml | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/doc/src/sgml/indices.sgml b/doc/src/sgml/indices.sgml index 3493f482b8..95c0a1926c 100644 --- a/doc/src/sgml/indices.sgml +++ b/doc/src/sgml/indices.sgml @@ -814,18 +814,20 @@ SELECT * FROM access_log WHERE url = '/index.html' AND client_ip = inet '212.78.10.32'; - A query that cannot use this index is: + Here the query's IP address is covered by the partial index. The + following query cannot use the partial index, as it uses an IP address + that is excluded from the index: SELECT * FROM access_log -WHERE client_ip = inet '192.168.100.23'; +WHERE url = '/index.html' AND client_ip = inet '192.168.100.23'; Observe that this kind of partial index requires that the common values be predetermined, so such partial indexes are best used for - data distributions that do not change. The indexes can be recreated + data distributions that do not change. Such indexes can be recreated occasionally to adjust for new data distributions, but this adds maintenance effort. -- 2.40.0