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Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/xoper.sgml | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/doc/src/sgml/xoper.sgml b/doc/src/sgml/xoper.sgml index 132056f869a..56b08491c96 100644 --- a/doc/src/sgml/xoper.sgml +++ b/doc/src/sgml/xoper.sgml @@ -283,6 +283,18 @@ column OP constant </para> <para> + Another useful built-in selectivity estimation function + is <function>matchingsel</function>, which will work for almost any + binary operator, if standard MCV and/or histogram statistics are + collected for the input data type(s). Its default estimate is set to + twice the default estimate used in <function>eqsel</function>, making + it most suitable for comparison operators that are somewhat less + strict than equality. (Or you could call the + underlying <function>generic_restriction_selectivity</function> + function, providing a different default estimate.) + </para> + + <para> There are additional selectivity estimation functions designed for geometric operators in <filename>src/backend/utils/adt/geo_selfuncs.c</filename>: <function>areasel</function>, <function>positionsel</function>, and <function>contsel</function>. At this writing these are just stubs, but you might want @@ -319,6 +331,7 @@ table1.column1 OP table2.column2 <member><function>scalarlejoinsel</function> for <literal><=</literal></member> <member><function>scalargtjoinsel</function> for <literal>></literal></member> <member><function>scalargejoinsel</function> for <literal>>=</literal></member> + <member><function>matchingjoinsel</function> for generic matching operators</member> <member><function>areajoinsel</function> for 2D area-based comparisons</member> <member><function>positionjoinsel</function> for 2D position-based comparisons</member> <member><function>contjoinsel</function> for 2D containment-based comparisons</member> |