PG_STATS¶
PG_STATS displays the single-column statistics stored in the pg_statistic table.
Name | Type | Reference | Description |
|---|---|---|---|
schemaname | name | PG_NAMESPACE.nspname | Name of the schema that contains the table |
tablename | name | PG_CLASS.relname | Name of the table |
attname | name | PG_ATTRIBUTE.attname | Column name |
inherited | boolean |
| Includes inherited sub-columns if the value is true; otherwise, 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 |
|
The negated form is used when ANALYZE believes that the number of distinct values is likely to increase as the table grows. The positive form is used when the column seems to have a fixed number of possible values. For example, -1 indicates a unique column in which the number of distinct values is the same as the number of rows. |
n_dndistinct | real |
| Number of unique non-null data values in the dn1 column
|
most_common_vals | anyarray |
| List of the most common values in a column. If this combination does not have the most common values, it will be NULL. |
most_common_freqs | real[] |
| List of the frequencies of the most common values, that is, the number of occurrences of each value divided by the 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 |
| Specifies a list of non-null element values most often appearing. |
most_common_elem_freqs | real[] |
| Specifies a list of the frequencies of the most common element values. |
elem_count_histogram | real[] |
| Specifies a histogram of the counts of distinct non-null element values. |