mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-09-10 05:59:23 +02:00
341 lines
8.8 KiB
Plaintext
341 lines
8.8 KiB
Plaintext
<!-- doc/src/sgml/pgstattuple.sgml -->
|
|
|
|
<sect1 id="pgstattuple" xreflabel="pgstattuple">
|
|
<title>pgstattuple</title>
|
|
|
|
<indexterm zone="pgstattuple">
|
|
<primary>pgstattuple</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <filename>pgstattuple</filename> module provides various functions to
|
|
obtain tuple-level statistics.
|
|
</para>
|
|
|
|
<sect2>
|
|
<title>Functions</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<indexterm>
|
|
<primary>pgstattuple</primary>
|
|
</indexterm>
|
|
|
|
<term>
|
|
<function>pgstattuple(text) returns record</>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>pgstattuple</function> returns a relation's physical length,
|
|
percentage of <quote>dead</> tuples, and other info. This may help users
|
|
to determine whether vacuum is necessary or not. The argument is the
|
|
target relation's name (optionally schema-qualified).
|
|
For example:
|
|
<programlisting>
|
|
test=> SELECT * FROM pgstattuple('pg_catalog.pg_proc');
|
|
-[ RECORD 1 ]------+-------
|
|
table_len | 458752
|
|
tuple_count | 1470
|
|
tuple_len | 438896
|
|
tuple_percent | 95.67
|
|
dead_tuple_count | 11
|
|
dead_tuple_len | 3157
|
|
dead_tuple_percent | 0.69
|
|
free_space | 8932
|
|
free_percent | 1.95
|
|
</programlisting>
|
|
The output columns are described in <xref linkend="pgstattuple-columns">.
|
|
</para>
|
|
|
|
<table id="pgstattuple-columns">
|
|
<title><function>pgstattuple</function> Output Columns</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Column</entry>
|
|
<entry>Type</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><structfield>table_len</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Physical relation length in bytes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>tuple_count</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Number of live tuples</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>tuple_len</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Total length of live tuples in bytes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>tuple_percent</structfield></entry>
|
|
<entry><type>float8</type></entry>
|
|
<entry>Percentage of live tuples</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>dead_tuple_count</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Number of dead tuples</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>dead_tuple_len</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Total length of dead tuples in bytes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>dead_tuple_percent</structfield></entry>
|
|
<entry><type>float8</type></entry>
|
|
<entry>Percentage of dead tuples</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>free_space</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Total free space in bytes</entry>
|
|
</row>
|
|
<row>
|
|
<entry><structfield>free_percent</structfield></entry>
|
|
<entry><type>float8</type></entry>
|
|
<entry>Percentage of free space</entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<function>pgstattuple</function> acquires only a read lock on the
|
|
relation. So the results do not reflect an instantaneous snapshot;
|
|
concurrent updates will affect them.
|
|
</para>
|
|
|
|
<para>
|
|
<function>pgstattuple</function> judges a tuple is <quote>dead</> if
|
|
<function>HeapTupleSatisfiesNow</> returns false.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>pgstattuple(oid) returns record</>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
This is the same as <function>pgstattuple(text)</function>, except
|
|
that the target relation is specified by OID.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<indexterm>
|
|
<primary>pgstatindex</primary>
|
|
</indexterm>
|
|
<function>pgstatindex(text) returns record</>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>pgstatindex</function> returns a record showing information
|
|
about a B-tree index. For example:
|
|
<programlisting>
|
|
test=> SELECT * FROM pgstatindex('pg_cast_oid_index');
|
|
-[ RECORD 1 ]------+------
|
|
version | 2
|
|
tree_level | 0
|
|
index_size | 8192
|
|
root_block_no | 1
|
|
internal_pages | 0
|
|
leaf_pages | 1
|
|
empty_pages | 0
|
|
deleted_pages | 0
|
|
avg_leaf_density | 50.27
|
|
leaf_fragmentation | 0
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The output columns are:
|
|
|
|
<informaltable>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Column</entry>
|
|
<entry>Type</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><structfield>version</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
<entry>B-tree version number</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>tree_level</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
<entry>Tree level of the root page</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>index_size</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Total number of pages in index</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>root_block_no</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Location of root block</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>internal_pages</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Number of <quote>internal</> (upper-level) pages</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>leaf_pages</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Number of leaf pages</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>empty_pages</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Number of empty pages</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>deleted_pages</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Number of deleted pages</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>avg_leaf_density</structfield></entry>
|
|
<entry><type>float8</type></entry>
|
|
<entry>Average density of leaf pages</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>leaf_fragmentation</structfield></entry>
|
|
<entry><type>float8</type></entry>
|
|
<entry>Leaf page fragmentation</entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
</para>
|
|
|
|
<para>
|
|
As with <function>pgstattuple</>, the results are accumulated
|
|
page-by-page, and should not be expected to represent an
|
|
instantaneous snapshot of the whole index.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<indexterm>
|
|
<primary>pgstatginindex</primary>
|
|
</indexterm>
|
|
<function>pgstatginindex(regclass) returns record</>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>pgstatginindex</function> returns a record showing information
|
|
about a GIN index. For example:
|
|
<programlisting>
|
|
test=> SELECT * FROM pgstatginindex('test_gin_index');
|
|
-[ RECORD 1 ]--+--
|
|
version | 1
|
|
pending_pages | 0
|
|
pending_tuples | 0
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
The output columns are:
|
|
|
|
<informaltable>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Column</entry>
|
|
<entry>Type</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><structfield>version</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
<entry>GIN version number</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>pending_pages</structfield></entry>
|
|
<entry><type>integer</type></entry>
|
|
<entry>Number of pages in the pending list</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><structfield>pending_tuples</structfield></entry>
|
|
<entry><type>bigint</type></entry>
|
|
<entry>Number of tuples in the pending list</entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<indexterm>
|
|
<primary>pg_relpages</primary>
|
|
</indexterm>
|
|
<function>pg_relpages(text) returns bigint</>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>pg_relpages</function> returns the number of pages in the
|
|
relation.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Authors</title>
|
|
|
|
<para>
|
|
Tatsuo Ishii and Satoshi Nagayasu
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|