pg_statistic_ext
#
The catalog <structname>pg_statistic_ext</structname>
holds definitions of extended planner statistics.
Each row in this catalog corresponds to a <firstterm>statistics object</firstterm>
created with <link linkend="sql-createstatistics"><command>CREATE STATISTICS</command></link>.
カタログpg_statistic_ext
はプランナの拡張統計情報の定義を保持します。
このカタログの各行はCREATE STATISTICS
で作成された統計オブジェクトに対応します。
表51.52 pg_statistic_ext
の列
Column Type 列 型 Description 説明 |
---|
Row identifier 行識別子 |
Table containing the columns described by this object このオブジェクトが記述する列を含むテーブル |
Name of the statistics object 統計オブジェクトの名前 |
The OID of the namespace that contains this statistics object この統計オブジェクトを含む名前空間のOID |
Owner of the statistics object 統計オブジェクトの所有者 |
An array of attribute numbers, indicating which table columns are
covered by this statistics object;
for example a value of <literal>1 3</literal> would
mean that the first and the third table columns are covered
属性番号の配列で、どのテーブル列が統計オブジェクトに含まれるかを示します。
例えば、値が |
<structfield>stxstattarget</structfield> controls the level of detail
of statistics accumulated for this statistics object by
<link linkend="sql-analyze"><command>ANALYZE</command></link>.
A zero value indicates that no statistics should be collected.
A null value says to use the maximum of the statistics targets of
the referenced columns, if set, or the system default statistics target.
Positive values of <structfield>stxstattarget</structfield>
determine the target number of <quote>most common values</quote>
to collect.
|
An array containing codes for the enabled statistics kinds;
valid values are:
<literal>d</literal> for n-distinct statistics,
<literal>f</literal> for functional dependency statistics,
<literal>m</literal> for most common values (MCV) list statistics, and
<literal>e</literal> for expression statistics
有効にされた統計種別のコードが入る配列です。
有効な値は:
|
Expression trees (in <function>nodeToString()</function>
representation) for statistics object attributes that are not simple
column references. This is a list with one element per expression.
Null if all statistics object attributes are simple references.
単純な列参照ではないオブジェクト属性の統計情報に対する( |
The <structname>pg_statistic_ext</structname> entry is filled in
completely during <link linkend="sql-createstatistics"><command>CREATE STATISTICS</command></link>, but the actual
statistical values are not computed then.
Subsequent <link linkend="sql-analyze"><command>ANALYZE</command></link> commands compute the desired values
and populate an entry in the
<link linkend="catalog-pg-statistic-ext-data"><structname>pg_statistic_ext_data</structname></link>
catalog.
CREATE STATISTICS
の実行中にpg_statistic_ext
エントリはすべて満たされますが、実際の統計データ値は計算されません。
あとで実行されるANALYZE
コマンドが必要な値を計算し、pg_statistic_ext_data
カタログのエントリに投入します。