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.