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Updated on 2023-10-23 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. (The current feature is a lab feature. Contact Huawei engineers for technical support before using it.) Statistics of expressions will be supported later. You can specify the extended statistics to collect. This system catalog is accessible only to users with the system administrator permission.

Table 1 PG_STATISTIC_EXT columns

Name

Type

Description

starelid

oid

Table or index that the described column belongs to.

starelkind

"char"

Type of an object. 'c' indicates a table, and 'p' indicates a partition.

stainherit

boolean

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

  • t (true): yes
  • f (false): no

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 all DNs.
  • A value greater than 0 is the actual number of distinct values.
  • A value less than 0 is the negative of a multiplier for the number of rows in the table. (For example, stadistinct=-0.5 indicates that values in a column appear twice on average.)
  • 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 negative of a multiplier for the number of rows in the table. (For example, stadistinct=-0.5 indicates that values in a column appear twice on average.)
  • 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.

Value range: 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.

Value range: 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.

Value range: 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.

Value range: 1 to 5

staexprs

pg_node_tree

Expression corresponding to the extended statistics information.

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: System Catalogs