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v3.0

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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 collect. This system catalog is accessible only to system administrators.

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 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 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.

NOTICE: 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.

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