diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/catalogs.sgml | 51 |
1 files changed, 40 insertions, 11 deletions
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index 180554b8e39..9564e012e66 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -5354,9 +5354,9 @@ Column data values of the appropriate kind for the <replaceable>N</>th <quote>slot</quote>, or null if the slot kind 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 - <type>anyarray</>. + values are actually of the specific column's data type, or a related + type such as an array's element type, so there is no way to define + these columns' type more specifically than <type>anyarray</>. </entry> </row> </tbody> @@ -8291,8 +8291,6 @@ <entry> A list of the most common values in the column. (Null if no values seem to be more common than any others.) - For some data types such as <type>tsvector</>, this is a list of - the most common element values rather than values of the type itself. </entry> </row> @@ -8301,12 +8299,9 @@ <entry><type>real[]</type></entry> <entry></entry> <entry> - A list of the frequencies of the most common values or elements, + A list of the frequencies of the most common values, i.e., number of occurrences of each divided by total number of rows. (Null when <structfield>most_common_vals</structfield> is.) - For some data types such as <type>tsvector</>, it can also store some - additional information, making it longer than the - <structfield>most_common_vals</> array. </entry> </row> @@ -8338,13 +8333,47 @@ type does not have a <literal><</> operator.) </entry> </row> + + <row> + <entry><structfield>most_common_elems</structfield></entry> + <entry><type>anyarray</type></entry> + <entry></entry> + <entry> + A list of non-null element values most often appearing within values of + the column. (Null for scalar types.) + </entry> + </row> + + <row> + <entry><structfield>most_common_elem_freqs</structfield></entry> + <entry><type>real[]</type></entry> + <entry></entry> + <entry> + A list of the frequencies of the most common element values, i.e., the + fraction of rows containing at least one instance of the given value. + Two or three additional values follow the per-element frequencies; + these are the minimum and maximum of the preceding per-element + frequencies, and optionally the frequency of null elements. + (Null when <structfield>most_common_elems</structfield> is.) + </entry> + </row> + + <row> + <entry><structfield>elem_count_histogram</structfield></entry> + <entry><type>real[]</type></entry> + <entry></entry> + <entry> + A histogram of the counts of distinct non-null element values within the + values of the column, followed by the average number of distinct + non-null elements. (Null for scalar types.) + </entry> + </row> </tbody> </tgroup> </table> <para> - The maximum number of entries in the <structfield>most_common_vals</> - and <structfield>histogram_bounds</> arrays can be set on a + The maximum number of entries in the array fields can be controlled on a column-by-column basis using the <command>ALTER TABLE SET STATISTICS</> command, or globally by setting the <xref linkend="guc-default-statistics-target"> run-time parameter. |