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Updated on 2024-06-03 GMT+08:00
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PG_STATISTIC_EXT

PG_STATISTIC_EXT displays extended statistics of tables in a database, such as statistics of multiple columns. Statistics of expressions will be supported later. You can specify the extended statistics to be collected. This system catalog is accessible only to the system administrator.

Table 1 PG_STATISTIC_EXT columns

Name

Type

Description

starelid

oid

Table or index that the described column belongs to.

starelkind

char

Type of the object to which a table belongs. 'c' indicates an ordinary table, and 'p' indicates a partitioned table.

stainherit

Boolean

Specifies whether to collect statistics for objects that have inheritance relationship.

stanullfrac

real

Percentage of column entries that are null.

stawidth

integer

Average stored width, in bytes, of non-null entries.

stadistinct

real
Number of distinct, non-null data values in the column for database nodes.
  • A value greater than 0 is the actual number of distinct values.
  • A value less than 0 is the ratio of the distinct value to the total number of rows. For example, if stadistinct is -0.5, the actual distinct value is the total number of rows multiplied by 0.5.
  • The value 0 indicates that the number of distinct values is unknown.

stadndistinct

real
Number of unique non-null data values in the DN1 column.
  • A value greater than 0 is the actual number of distinct values.
  • A value less than 0 is the ratio of the distinct value to the total number of rows. For example, if stadistinct is -0.5, the actual distinct value is the total number of rows multiplied by 0.5.
  • The value 0 indicates that the number of distinct values is unknown.

stakindN

smallint

Code number stating that the type of statistics is stored in slot N of the pg_statistic row.

The value of N ranges from 1 to 5.

staopN

oid

Operator used to generate the statistics stored in slot N. For example, a histogram slot shows the < operator that defines the sort order of the data.

The value of N ranges from 1 to 5.

stakey

int2vector

Array of a column ID.

stanumbersN

real[]

Numerical statistics of the appropriate type for slot N. The value is NULL if the slot does not involve numerical values.

The value of N ranges from 1 to 5.

stavaluesN

anyarray

Column data values of the appropriate type for slot N. The value is NULL if the slot type does not store any data values. Each array's element values are actually of the specific column's data type so there is no way to define these columns' type more specifically than anyarray.

The value of N ranges from 1 to 5.

staexprs

pg_node_tree

Expression corresponding to the extended statistics information.

stasource

char
Source of extended statistics:
  • 'a': indicates that the statistics data is automatically created, which is controlled by the GUC parameter auto_statistic_ext_columns.
  • 'm': indicates that a user manually creates the statistics data using analyze tablename ((column list)) or alter table tablename add statistics ((column list)).

stastatus

char
Status of extended statistics:
  • 'a': active and available.
  • 'd': disabled. Related information is not collected, and the optimizer does not use the data when generating a plan. You can use the alter table tablename disable/enable statistics((column list)) syntax to modify the status of extended statistics.

staextname

name

Alias of the multi-column group of multi-column statistics.

stastate

"char"

Specifies whether the statistics are locked. If the statistics are locked, they cannot be updated.

  • l: locked
  • u: unlocked

PG_STATISTIC_EXT stores sensitive information about statistical objects, such as MCVs. The system administrator and authorized users can access the PG_STATISTIC_EXT system catalog to query the sensitive information about the statistical objects.

Parent topic: Other System Catalogs