PG_STATS

PG_STATS provides access to the single-column statistics stored in the pg_statistic table. The autovacuum_naptime parameter specifies the interval for updating statistics recorded in the view.

Table 1 PG_STATS columns

Name	Type	Reference	Description
schemaname	name	PG_NAMESPACE.nspname	Name of the schema that contains a table
tablename	name	PG_CLASS.relname	Table name
attname	name	PG_ATTRIBUTE.attname	Field name
inherited	Boolean	-	Includes inherited sub-columns if the value is true; otherwise, it indicates the column in a specified table.
null_frac	real	-	Percentage of column entries that are null
avg_width	integer	-	Average width in bytes of column's entries
n_distinct	real	-	- Estimated number of distinct values in the column if the value is greater than 0 - Negative of the number of distinct values divided by the number of rows if the value is less than 0 1. The negated form is used when ANALYZE believes that the number of distinct values is likely to increase as the table grows. 2. The positive form is used when the column seems to have a fixed number of possible values. For example, -1 indicates that the number of distinct values is the same as the number of rows for a unique column.
n_dndistinct	real	-	Number of unique non-null data values in the dn1 column - Exact number of distinct values if the value is greater than 0. - Negative of the number of distinct values divided by the number of rows if the value is less than 0 For example, if the value of a column appears twice in average, set n_dndistinct=-0.5. - The number of distinct values is unknown if the value is 0.
most_common_vals	anyarray	-	List of the most common values in a column. (NULL if no values in the column seem to be more common than any others)
most_common_freqs	real[]	-	List of the frequencies of the most common values, that is, number of occurrences of each divided by total number of rows. (NULL if most_common_vals is NULL)
histogram_bounds	anyarray	-	List of values that divide the column's values into groups of equal proportion. The values in most_common_vals, if present, are omitted from this histogram calculation. This field is null if the field data type does not have a < operator or if the most_common_vals list accounts for the entire population.
correlation	real	-	Statistical correlation between physical row ordering and logical ordering of the column values. It ranges from -1 to +1. When the value is near to -1 or +1, an index scan on the column is estimated to be cheaper than when it is near to zero, due to reduction of random access to the disk. This column is null if the column data type does not have a < operator.
most_common_elems	anyarray	-	A list of non-null element values most often appearing
most_common_elem_freqs	real[]	-	A list of the frequencies of the most common element values
elem_count_histogram	real[]	-	A histogram of the counts of distinct non-null element values