diff options
| author | Bruce Momjian <bruce@momjian.us> | 2021-12-22 16:29:16 -0500 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 2021-12-22 16:29:16 -0500 |
| commit | 2ff209953e0a7b4ce9df1c1ba15783345ef5659f (patch) | |
| tree | 3c60456bf9cb2e6f486313a40ae91229bb96c43e | |
| parent | 420f9ac1b77cca142d4ab7919a4f2b703c1278b8 (diff) | |
| download | postgresql-2ff209953e0a7b4ce9df1c1ba15783345ef5659f.tar.gz postgresql-2ff209953e0a7b4ce9df1c1ba15783345ef5659f.zip | |
doc: clarify when expression indexes evaluate their expressions
Only non-HOT updates evaluate the index expression.
Reported-by: Chris Lowder
Discussion: https://postgr.es/m/163967385701.26064.15365003480975321072@wrigleys.postgresql.org
Backpatch-through: 10
| -rw-r--r-- | doc/src/sgml/indices.sgml | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/doc/src/sgml/indices.sgml b/doc/src/sgml/indices.sgml index 56fbd451783..023157d8884 100644 --- a/doc/src/sgml/indices.sgml +++ b/doc/src/sgml/indices.sgml @@ -748,8 +748,8 @@ CREATE INDEX people_names ON people ((first_name || ' ' || last_name)); <para> Index expressions are relatively expensive to maintain, because the - derived expression(s) must be computed for each row upon insertion - and whenever it is updated. However, the index expressions are + derived expression(s) must be computed for each row insertion + and non-HOT update. However, the index expressions are <emphasis>not</emphasis> recomputed during an indexed search, since they are already stored in the index. In both examples above, the system sees the query as just <literal>WHERE indexedcolumn = 'constant'</literal> |