diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/system-views.sgml | 294 |
1 files changed, 294 insertions, 0 deletions
diff --git a/doc/src/sgml/system-views.sgml b/doc/src/sgml/system-views.sgml index 3f5a306247e..e9a59af8c34 100644 --- a/doc/src/sgml/system-views.sgml +++ b/doc/src/sgml/system-views.sgml @@ -52,6 +52,11 @@ <tbody> <row> + <entry><link linkend="view-pg-aios"><structname>pg_aios</structname></link></entry> + <entry>In-use asynchronous IO handles</entry> + </row> + + <row> <entry><link linkend="view-pg-available-extensions"><structname>pg_available_extensions</structname></link></entry> <entry>available extensions</entry> </row> @@ -231,6 +236,295 @@ </table> </sect1> + <sect1 id="view-pg-aios"> + <title><structname>pg_aios</structname></title> + + <indexterm zone="view-pg-aios"> + <primary>pg_aios</primary> + </indexterm> + + <para> + The <structname>pg_aios</structname> view lists all <xref + linkend="glossary-aio"/> handles that are currently in-use. An I/O handle + is used to reference an I/O operation that is being prepared, executed or + is in the process of completing. <structname>pg_aios</structname> contains + one row for each I/O handle. + </para> + + <para> + This view is mainly useful for developers of + <productname>PostgreSQL</productname>, but may also be useful when tuning + <productname>PostgreSQL</productname>. + </para> + + <table> + <title><structname>pg_aios</structname> Columns</title> + <tgroup cols="1"> + <thead> + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + Column Type + </para> + <para> + Description + </para></entry> + </row> + </thead> + + <tbody> + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>pid</structfield> <type>int4</type> + </para> + <para> + Process ID of the server process that is issuing this I/O. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>io_id</structfield> <type>int4</type> + </para> + <para> + Identifier of the I/O handle. Handles are reused once the I/O + completed (or if the handle is released before I/O is started). On reuse + <link linkend="view-pg-aios-io-generation"> + <structname>pg_aios</structname>.<structfield>io_generation</structfield> + </link> + is incremented. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry" id="view-pg-aios-io-generation"><para role="column_definition"> + <structfield>io_generation</structfield> <type>int8</type> + </para> + <para> + Generation of the I/O handle. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>state</structfield> <type>text</type> + </para> + <para> + State of the I/O handle: + <itemizedlist> + <listitem> + <para> + <literal>HANDED_OUT</literal>, referenced by code but not yet used + </para> + </listitem> + <listitem> + <para> + <literal>DEFINED</literal>, information necessary for execution is known + </para> + </listitem> + <listitem> + <para> + <literal>STAGED</literal>, ready for execution + </para> + </listitem> + <listitem> + <para> + <literal>SUBMITTED</literal>, submitted for execution + </para> + </listitem> + <listitem> + <para> + <literal>COMPLETED_IO</literal>, finished, but result has not yet been processed + </para> + </listitem> + <listitem> + <para> + <literal>COMPLETED_SHARED</literal>, shared completion processing completed + </para> + </listitem> + <listitem> + <para> + <literal>COMPLETED_LOCAL</literal>, backend local completion processing completed + </para> + </listitem> + </itemizedlist> + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>operation</structfield> <type>text</type> + </para> + <para> + Operation performed using the I/O handle: + <itemizedlist> + <listitem> + <para> + <literal>invalid</literal>, not yet known + </para> + </listitem> + <listitem> + <para> + <literal>readv</literal>, a vectored read + </para> + </listitem> + <listitem> + <para> + <literal>writev</literal>, a vectored write + </para> + </listitem> + </itemizedlist> + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>off</structfield> <type>int8</type> + </para> + <para> + Offset of the I/O operation. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>length</structfield> <type>int8</type> + </para> + <para> + Length of the I/O operation. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>target</structfield> <type>text</type> + </para> + <para> + What kind of object is the I/O targeting: + <itemizedlist spacing="compact"> + <listitem> + <para> + <literal>smgr</literal>, I/O on relations + </para> + </listitem> + </itemizedlist> + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>handle_data_len</structfield> <type>int2</type> + </para> + <para> + Length of the data associated with the I/O operation. For I/O to/from + <xref linkend="guc-shared-buffers"/> and <xref + linkend="guc-temp-buffers"/>, this indicates the number of buffers the + I/O is operating on. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>raw_result</structfield> <type>int4</type> + </para> + <para> + Low-level result of the I/O operation, or NULL if the operation has not + yet completed. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>result</structfield> <type>text</type> + </para> + <para> + High-level result of the I/O operation: + <itemizedlist> + <listitem> + <para> + <literal>UNKNOWN</literal> means that the result of the + operation is not yet known. + </para> + </listitem> + <listitem> + <para> + <literal>OK</literal> means the I/O completed successfully. + </para> + </listitem> + <listitem> + <para> + <literal>PARTIAL</literal> means that the I/O completed without + error, but did not process all data. Commonly callers will need to + retry and perform the remainder of the work in a separate I/O. + </para> + </listitem> + <listitem> + <para> + <literal>WARNING</literal> means that the I/O completed without + error, but that execution of the IO triggered a warning. E.g. when + encountering a corrupted buffer with <xref + linkend="guc-zero-damaged-pages"/> enabled. + </para> + </listitem> + <listitem> + <para> + <literal>ERROR</literal> means the I/O failed with an error. + </para> + </listitem> + </itemizedlist> + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>target_desc</structfield> <type>text</type> + </para> + <para> + Description of what the I/O operation is targeting. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>f_sync</structfield> <type>bool</type> + </para> + <para> + Flag indicating whether the I/O is executed synchronously. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>f_localmem</structfield> <type>bool</type> + </para> + <para> + Flag indicating whether the I/O references process local memory. + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>f_buffered</structfield> <type>bool</type> + </para> + <para> + Flag indicating whether the I/O is buffered I/O. + </para></entry> + </row> + + </tbody> + </tgroup> + </table> + + <para> + The <structname>pg_aios</structname> view is read-only. + </para> + + <para> + By default, the <structname>pg_aios</structname> view can be read only by + superusers or roles with privileges of the + <literal>pg_read_all_stats</literal> role. + </para> + </sect1> + <sect1 id="view-pg-available-extensions"> <title><structname>pg_available_extensions</structname></title> |