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

GS_STATISTIC_HISTORY

GS_STATISTIC_HISTORY is a single-column historical statistics management table that stores historical statistics about tables and index columns in a database. This table is visible and unavailable in distributed mode.

Table 1 GS_STATISTIC_HISTORY 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

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

statimestamp

timestamp with time zone

Time when the statistics are collected.

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.

standvfunc

"char"

Algorithm used to calculate the NDV based on the statistics.

  • d: The original DUJ1 algorithm is used for estimation.
  • c: The C19 algorithm is used for estimation.

staorigin

"char"

Source of the statistics collection mode.

  • a: The collection is triggered by AUTOANALYZE.
  • m: The collection is triggered by manual ANALYZE.
  • g: The gsstat thread is triggered to perform ANALYZE collection when a large amount of data is inserted.

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.

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.

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 stadndistinct 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.

staextinfo

text

Information about extension statistics. Reserved column.