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v3.1

Documentation:v3.1

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PG_STATISTIC

PG_STATISTIC stores statistics about tables and index columns in a database. By default, only the system administrator can access the system catalog. Common users can access the system catalog only after being authorized.

Table 1 PG_STATISTIC columns

Name Type Description
starelid oid Table or index that the described column belongs to
starelkind "char" Type of an object
staattnum smallint Number of the described column in the table, starting from 1
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.
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
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
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.
staextinfo text Information about extension statistics. This is reserved.

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

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