diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/xindex.sgml | 3 | ||||
| -rw-r--r-- | doc/src/sgml/xoper.sgml | 35 |
2 files changed, 16 insertions, 22 deletions
diff --git a/doc/src/sgml/xindex.sgml b/doc/src/sgml/xindex.sgml index 745b4d5619a..b951a58e0ab 100644 --- a/doc/src/sgml/xindex.sgml +++ b/doc/src/sgml/xindex.sgml @@ -801,8 +801,7 @@ CREATE OPERATOR < ( It is important to specify the correct commutator and negator operators, as well as suitable restriction and join selectivity functions, otherwise the optimizer will be unable to make effective - use of the index. Note that the less-than, equal, and - greater-than cases should use different selectivity functions. + use of the index. </para> <para> diff --git a/doc/src/sgml/xoper.sgml b/doc/src/sgml/xoper.sgml index 8568e21216b..d484d80105e 100644 --- a/doc/src/sgml/xoper.sgml +++ b/doc/src/sgml/xoper.sgml @@ -242,20 +242,11 @@ column OP constant <simplelist> <member><function>eqsel</> for <literal>=</></member> <member><function>neqsel</> for <literal><></></member> - <member><function>scalarltsel</> for <literal><</> or <literal><=</></member> - <member><function>scalargtsel</> for <literal>></> or <literal>>=</></member> - </simplelist> - It might seem a little odd that these are the categories, but they - make sense if you think about it. <literal>=</> will typically accept only - a small fraction of the rows in a table; <literal><></> will typically reject - only a small fraction. <literal><</> will accept a fraction that depends on - where the given constant falls in the range of values for that table - column (which, it just so happens, is information collected by - <command>ANALYZE</command> and made available to the selectivity estimator). - <literal><=</> will accept a slightly larger fraction than <literal><</> for the same - comparison constant, but they're close enough to not be worth - distinguishing, especially since we're not likely to do better than a - rough guess anyhow. Similar remarks apply to <literal>></> and <literal>>=</>. + <member><function>scalarltsel</> for <literal><</></member> + <member><function>scalarlesel</> for <literal><=</></member> + <member><function>scalargtsel</> for <literal>></></member> + <member><function>scalargesel</> for <literal>>=</></member> + </simplelist> </para> <para> @@ -267,10 +258,12 @@ column OP constant </para> <para> - You can use <function>scalarltsel</> and <function>scalargtsel</> for comparisons on data types that - have some sensible means of being converted into numeric scalars for - range comparisons. If possible, add the data type to those understood - by the function <function>convert_to_scalar()</function> in <filename>src/backend/utils/adt/selfuncs.c</filename>. + You can use <function>scalarltsel</>, <function>scalarlesel</>, + <function>scalargtsel</> and <function>scalargesel</> for comparisons on + data types that have some sensible means of being converted into numeric + scalars for range comparisons. If possible, add the data type to those + understood by the function <function>convert_to_scalar()</function> in + <filename>src/backend/utils/adt/selfuncs.c</filename>. (Eventually, this function should be replaced by per-data-type functions identified through a column of the <classname>pg_type</> system catalog; but that hasn't happened yet.) If you do not do this, things will still work, but the optimizer's @@ -310,8 +303,10 @@ table1.column1 OP table2.column2 <simplelist> <member><function>eqjoinsel</> for <literal>=</></member> <member><function>neqjoinsel</> for <literal><></></member> - <member><function>scalarltjoinsel</> for <literal><</> or <literal><=</></member> - <member><function>scalargtjoinsel</> for <literal>></> or <literal>>=</></member> + <member><function>scalarltjoinsel</> for <literal><</></member> + <member><function>scalarlejoinsel</> for <literal><=</></member> + <member><function>scalargtjoinsel</> for <literal>></></member> + <member><function>scalargejoinsel</> for <literal>>=</></member> <member><function>areajoinsel</> for 2D area-based comparisons</member> <member><function>positionjoinsel</> for 2D position-based comparisons</member> <member><function>contjoinsel</> for 2D containment-based comparisons</member> |