diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/catalogs.sgml | 37 |
1 files changed, 33 insertions, 4 deletions
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index 82d3658a50b..0acd79361bd 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.214 2009/12/17 14:36:15 rhaas Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.215 2009/12/29 20:11:42 tgl Exp $ --> <!-- Documentation of the system catalogs, directed toward PostgreSQL developers --> @@ -4506,19 +4506,32 @@ The catalog <structname>pg_statistic</structname> stores statistical data about the contents of the database. Entries are created by <xref linkend="sql-analyze" endterm="sql-analyze-title"> - and subsequently used by the query planner. There is one entry for - each table column that has been analyzed. Note that all the + and subsequently used by the query planner. Note that all the statistical data is inherently approximate, even assuming that it is up-to-date. </para> <para> + Normally there is one entry, with <structfield>stainherit</> = + <literal>false</>, for each table column that has been analyzed. + If the table has inheritance children, a second entry with + <structfield>stainherit</> = <literal>true</> is also created. This row + represents the column's statistics over the inheritance tree, i.e., + statistics for the data you'd see with + <literal>SELECT <replaceable>column</> FROM <replaceable>table</>*</literal>, + whereas the <structfield>stainherit</> = <literal>false</> row represents + the results of + <literal>SELECT <replaceable>column</> FROM ONLY <replaceable>table</></literal>. + </para> + + <para> <structname>pg_statistic</structname> also stores statistical data about the values of index expressions. These are described as if they were actual data columns; in particular, <structfield>starelid</structfield> references the index. No entry is made for an ordinary non-expression index column, however, since it would be redundant with the entry - for the underlying table column. + for the underlying table column. Currently, entries for index expressions + always have <structfield>stainherit</> = <literal>false</>. </para> <para> @@ -4573,6 +4586,14 @@ </row> <row> + <entry><structfield>stainherit</structfield></entry> + <entry><type>bool</type></entry> + <entry></entry> + <entry>If true, the stats include inheritance child columns, not just the + values in the specified relation</entry> + </row> + + <row> <entry><structfield>stanullfrac</structfield></entry> <entry><type>float4</type></entry> <entry></entry> @@ -7115,6 +7136,14 @@ </row> <row> + <entry><structfield>inherited</structfield></entry> + <entry><type>bool</type></entry> + <entry></entry> + <entry>If true, this row includes inheritance child columns, not just the + values in the specified table</entry> + </row> + + <row> <entry><structfield>null_frac</structfield></entry> <entry><type>real</type></entry> <entry></entry> |