pg_statistic_ext - PolarDB - Alibaba Cloud Documentation Center

The catalog pg_statistic_ext holds definitions of extended planner statistics. Each row in this catalog corresponds to a statistics object created with CREATE STATISTICS.

Column	Type	Description
`oid`	`oid`	Row identifier.
`stxrelid`	`oid`	Table containing the columns described by this object.
`stxname`	`name`	Name of the statistics object.
`stxnamespace`	`oid`	The OID of the namespace that contains this statistics object.
`stxowner`	`oid`	Owner of the statistics object.
`stxstattarget`	`int4`	`stxstattarget` controls the level of detail of statistics accumulated for this statistics object by ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the maximum of the statistics targets of the referenced columns, if set, or the system default statistics target. Positive values of `stxstattarget` determine the target number of“most common values”to collect.
`stxkeys`	`int2vector`	An array of attribute numbers, indicating which table columns are covered by this statistics object; for example a value of `1 3` would mean that the first and the third table columns are covered.
`stxkind`	`char[]`	An array containing codes for the enabled statistics kinds; valid values are:`d` for n-distinct statistics,`f` for functional dependency statistics,`m` for most common values (MCV) list statistics, and `e` for expression statistics.

The pg_statistic_ext entry is filled in completely during CREATE STATISTICS, but the actual statistical values are not computed then. Subsequent ANALYZE commands compute the desired values and populate an entry in the pg_statistic_ext_data catalog.