51.50. pg_statistic_ext

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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.

Table 51.50. pg_statistic_ext Columns

Column Type Description

oid oid Row identifier

stxrelid oid (references pg_class.oid) Table containing the columns described by this object

stxname name Name of the statistics object

stxnamespace oid (references pg_namespace.oid) The OID of the namespace that contains this statistics object

stxowner oid (references pg_authid.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 (references pg_attribute.attnum) 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 statistic kinds; valid values are: d for n-distinct statistics, f for functional dependency statistics, and m for most common values (MCV) list 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.