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diff --git a/doc/src/sgml/html/pgwalinspect.html b/doc/src/sgml/html/pgwalinspect.html new file mode 100644 index 0000000..b26b30c --- /dev/null +++ b/doc/src/sgml/html/pgwalinspect.html @@ -0,0 +1,130 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>F.37. pg_walinspect</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="pgvisibility.html" title="F.36. pg_visibility" /><link rel="next" href="postgres-fdw.html" title="F.38. postgres_fdw" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.37. pg_walinspect</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgvisibility.html" title="F.36. pg_visibility">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="postgres-fdw.html" title="F.38. postgres_fdw">Next</a></td></tr></table><hr /></div><div class="sect1" id="PGWALINSPECT"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.37. pg_walinspect</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="pgwalinspect.html#id-1.11.7.46.8">F.37.1. General Functions</a></span></dt><dt><span class="sect2"><a href="pgwalinspect.html#id-1.11.7.46.9">F.37.2. Author</a></span></dt></dl></div><a id="id-1.11.7.46.2" class="indexterm"></a><p> + The <code class="filename">pg_walinspect</code> module provides SQL functions that + allow you to inspect the contents of write-ahead log of + a running <span class="productname">PostgreSQL</span> database cluster at a low + level, which is useful for debugging, analytical, reporting or + educational purposes. It is similar to <a class="xref" href="pgwaldump.html" title="pg_waldump"><span class="refentrytitle"><span class="application">pg_waldump</span></span></a>, but + accessible through SQL rather than a separate utility. + </p><p> + All the functions of this module will provide the WAL information using the + current server's timeline ID. + </p><p> + All the functions of this module will try to find the first valid WAL record + that is at or after the given <em class="replaceable"><code>in_lsn</code></em> or + <em class="replaceable"><code>start_lsn</code></em> and will emit error if no such record + is available. Similarly, the <em class="replaceable"><code>end_lsn</code></em> must be + available, and if it falls in the middle of a record, the entire record must + be available. + </p><div class="note"><h3 class="title">Note</h3><p> + Some functions, such as <code class="function"><a class="link" href="functions-admin.html#PG-LOGICAL-EMIT-MESSAGE">pg_logical_emit_message</a></code>, + return the LSN <span class="emphasis"><em>after</em></span> the record just + inserted. Therefore, if you pass that LSN as + <em class="replaceable"><code>in_lsn</code></em> or <em class="replaceable"><code>start_lsn</code></em> + to one of these functions, it will return the <span class="emphasis"><em>next</em></span> + record. + </p></div><p> + By default, use of these functions is restricted to superusers and members of + the <code class="literal">pg_read_server_files</code> role. Access may be granted by + superusers to others using <code class="command">GRANT</code>. + </p><div class="sect2" id="id-1.11.7.46.8"><div class="titlepage"><div><div><h3 class="title">F.37.1. General Functions</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term"> + <code class="function">pg_get_wal_record_info(in_lsn pg_lsn) returns record</code> + </span></dt><dd><p> + Gets WAL record information of a given LSN. If the given LSN isn't + at the start of a WAL record, it gives the information of the next + available valid WAL record; or an error if no such record is found. + For example, usage of the function is as + follows: +</p><pre class="screen"> +postgres=# SELECT * FROM pg_get_wal_record_info('0/1E826E98'); +-[ RECORD 1 ]----+---------------------------------------------------- +start_lsn | 0/1E826F20 +end_lsn | 0/1E826F60 +prev_lsn | 0/1E826C80 +xid | 0 +resource_manager | Heap2 +record_type | PRUNE +record_length | 58 +main_data_length | 8 +fpi_length | 0 +description | snapshotConflictHorizon 33748 nredirected 0 ndead 2 +block_ref | blkref #0: rel 1663/5/60221 fork main blk 2 +</pre><p> + </p></dd><dt><span class="term"> + <code class="function"> + pg_get_wal_records_info(start_lsn pg_lsn, end_lsn pg_lsn) + returns setof record + </code> + </span></dt><dd><p> + Gets information of all the valid WAL records between + <em class="replaceable"><code>start_lsn</code></em> and <em class="replaceable"><code>end_lsn</code></em>. + Returns one row per WAL record. If <em class="replaceable"><code>start_lsn</code></em> + or <em class="replaceable"><code>end_lsn</code></em> are not yet available, the + function will raise an error. For example: +</p><pre class="screen"> +postgres=# SELECT * FROM pg_get_wal_records_info('0/1E913618', '0/1E913740') LIMIT 1; +-[ RECORD 1 ]----+-------------------------------------------------------------- +start_lsn | 0/1E913618 +end_lsn | 0/1E913650 +prev_lsn | 0/1E9135A0 +xid | 0 +resource_manager | Standby +record_type | RUNNING_XACTS +record_length | 50 +main_data_length | 24 +fpi_length | 0 +description | nextXid 33775 latestCompletedXid 33774 oldestRunningXid 33775 +block_ref | +</pre><p> + </p></dd><dt><span class="term"> + <code class="function"> + pg_get_wal_records_info_till_end_of_wal(start_lsn pg_lsn) + returns setof record + </code> + </span></dt><dd><p> + This function is the same as <code class="function">pg_get_wal_records_info()</code>, + except that it gets information of all the valid WAL records from + <em class="replaceable"><code>start_lsn</code></em> till the end of WAL. + </p></dd><dt><span class="term"> + <code class="function"> + pg_get_wal_stats(start_lsn pg_lsn, end_lsn pg_lsn, per_record boolean DEFAULT false) + returns setof record + </code> + </span></dt><dd><p> + Gets statistics of all the valid WAL records between + <em class="replaceable"><code>start_lsn</code></em> and + <em class="replaceable"><code>end_lsn</code></em>. By default, it returns one row per + <em class="replaceable"><code>resource_manager</code></em> type. When + <em class="replaceable"><code>per_record</code></em> is set to <code class="literal">true</code>, + it returns one row per <em class="replaceable"><code>record_type</code></em>. + If <em class="replaceable"><code>start_lsn</code></em> + or <em class="replaceable"><code>end_lsn</code></em> are not yet available, the + function will raise an error. For example: +</p><pre class="screen"> +postgres=# SELECT * FROM pg_get_wal_stats('0/1E847D00', '0/1E84F500') + WHERE count > 0 AND + "resource_manager/record_type" = 'Transaction' + LIMIT 1; +-[ RECORD 1 ]----------------+------------------- +resource_manager/record_type | Transaction +count | 2 +count_percentage | 8 +record_size | 875 +record_size_percentage | 41.23468426013195 +fpi_size | 0 +fpi_size_percentage | 0 +combined_size | 875 +combined_size_percentage | 2.8634072910530795 +</pre><p> + </p></dd><dt><span class="term"> + <code class="function"> + pg_get_wal_stats_till_end_of_wal(start_lsn pg_lsn, per_record boolean DEFAULT false) + returns setof record + </code> + </span></dt><dd><p> + This function is the same as <code class="function">pg_get_wal_stats()</code>, + except that it gets statistics of all the valid WAL records from + <em class="replaceable"><code>start_lsn</code></em> till end of WAL. + </p></dd></dl></div></div><div class="sect2" id="id-1.11.7.46.9"><div class="titlepage"><div><div><h3 class="title">F.37.2. Author</h3></div></div></div><p> + Bharath Rupireddy <code class="email"><<a class="email" href="mailto:bharath.rupireddyforpostgres@gmail.com">bharath.rupireddyforpostgres@gmail.com</a>></code> + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgvisibility.html" title="F.36. pg_visibility">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="postgres-fdw.html" title="F.38. postgres_fdw">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.36. pg_visibility </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.38. postgres_fdw</td></tr></table></div></body></html>
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