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Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/spgist.sgml | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/doc/src/sgml/spgist.sgml b/doc/src/sgml/spgist.sgml index 0202dbcdd5a..fd312cf4368 100644 --- a/doc/src/sgml/spgist.sgml +++ b/doc/src/sgml/spgist.sgml @@ -100,6 +100,18 @@ value when that is needed. </para> + <note> + <para> + The <acronym>SP-GiST</acronym> core code takes care of NULL entries. + Although <acronym>SP-GiST</acronym> indexes do store entries for nulls + in indexed columns, this is hidden from the index operator class code: + no null index entries or search conditions will ever be passed to the + operator class methods. (It is assumed that <acronym>SP-GiST</acronym> + operators are strict and so cannot succeed for NULL values.) NULLs + are therefore not discussed further here. + </para> + </note> + <para> There are five user-defined methods that an index operator class for <acronym>SP-GiST</acronym> must provide. All five follow the convention |