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| 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 | 9ac9878f15c993a8cbe3025a1ff7b72225841029 (patch) | |
| tree | 59e70e7e5a0653f163d39fe0481c3a7772d278e1 | |
| parent | 861095a40987fb40d0e3ed43f223ca0f79071dea (diff) | |
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 56fd0a3d3d3..738d9a87c58 100644 --- a/doc/src/sgml/indices.sgml +++ b/doc/src/sgml/indices.sgml @@ -733,8 +733,8 @@ 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> |