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diff --git a/doc/src/sgml/html/pgprewarm.html b/doc/src/sgml/html/pgprewarm.html new file mode 100644 index 0000000..2c5ef9e --- /dev/null +++ b/doc/src/sgml/html/pgprewarm.html @@ -0,0 +1,82 @@ +<?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.28. pg_prewarm</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="pgfreespacemap.html" title="F.27. pg_freespacemap" /><link rel="next" href="pgrowlocks.html" title="F.29. pgrowlocks" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.28. pg_prewarm</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgfreespacemap.html" title="F.27. pg_freespacemap">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 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pgrowlocks.html" title="F.29. pgrowlocks">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="PGPREWARM"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.28. pg_prewarm</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="pgprewarm.html#id-1.11.7.37.4">F.28.1. Functions</a></span></dt><dt><span class="sect2"><a href="pgprewarm.html#id-1.11.7.37.5">F.28.2. Configuration Parameters</a></span></dt><dt><span class="sect2"><a href="pgprewarm.html#id-1.11.7.37.6">F.28.3. Author</a></span></dt></dl></div><a id="id-1.11.7.37.2" class="indexterm"></a><p> + The <code class="filename">pg_prewarm</code> module provides a convenient way + to load relation data into either the operating system buffer cache + or the <span class="productname">PostgreSQL</span> buffer cache. Prewarming + can be performed manually using the <code class="filename">pg_prewarm</code> function, + or can be performed automatically by including <code class="literal">pg_prewarm</code> in + <a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a>. In the latter case, the + system will run a background worker which periodically records the contents + of shared buffers in a file called <code class="filename">autoprewarm.blocks</code> and + will, using 2 background workers, reload those same blocks after a restart. + </p><div class="sect2" id="id-1.11.7.37.4"><div class="titlepage"><div><div><h3 class="title">F.28.1. Functions</h3></div></div></div><pre class="synopsis"> +pg_prewarm(regclass, mode text default 'buffer', fork text default 'main', + first_block int8 default null, + last_block int8 default null) RETURNS int8 +</pre><p> + The first argument is the relation to be prewarmed. The second argument + is the prewarming method to be used, as further discussed below; the third + is the relation fork to be prewarmed, usually <code class="literal">main</code>. + The fourth argument is the first block number to prewarm + (<code class="literal">NULL</code> is accepted as a synonym for zero). The fifth + argument is the last block number to prewarm (<code class="literal">NULL</code> + means prewarm through the last block in the relation). The return value + is the number of blocks prewarmed. + </p><p> + There are three available prewarming methods. <code class="literal">prefetch</code> + issues asynchronous prefetch requests to the operating system, if this is + supported, or throws an error otherwise. <code class="literal">read</code> reads + the requested range of blocks; unlike <code class="literal">prefetch</code>, this is + synchronous and supported on all platforms and builds, but may be slower. + <code class="literal">buffer</code> reads the requested range of blocks into the + database buffer cache. + </p><p> + Note that with any of these methods, attempting to prewarm more blocks than + can be cached — by the OS when using <code class="literal">prefetch</code> or + <code class="literal">read</code>, or by <span class="productname">PostgreSQL</span> when + using <code class="literal">buffer</code> — will likely result in lower-numbered + blocks being evicted as higher numbered blocks are read in. Prewarmed data + also enjoys no special protection from cache evictions, so it is possible + that other system activity may evict the newly prewarmed blocks shortly + after they are read; conversely, prewarming may also evict other data from + cache. For these reasons, prewarming is typically most useful at startup, + when caches are largely empty. + </p><pre class="synopsis"> +autoprewarm_start_worker() RETURNS void +</pre><p> + Launch the main autoprewarm worker. This will normally happen + automatically, but is useful if automatic prewarm was not configured at + server startup time and you wish to start up the worker at a later time. + </p><pre class="synopsis"> +autoprewarm_dump_now() RETURNS int8 +</pre><p> + Update <code class="filename">autoprewarm.blocks</code> immediately. This may be useful + if the autoprewarm worker is not running but you anticipate running it + after the next restart. The return value is the number of records written + to <code class="filename">autoprewarm.blocks</code>. + </p></div><div class="sect2" id="id-1.11.7.37.5"><div class="titlepage"><div><div><h3 class="title">F.28.2. Configuration Parameters</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term"> + <code class="varname">pg_prewarm.autoprewarm</code> (<code class="type">boolean</code>) + <a id="id-1.11.7.37.5.2.1.1.3" class="indexterm"></a> + </span></dt><dd><p> + Controls whether the server should run the autoprewarm worker. This is + on by default. This parameter can only be set at server start. + </p></dd></dl></div><div class="variablelist"><dl class="variablelist"><dt><span class="term"> + <code class="varname">pg_prewarm.autoprewarm_interval</code> (<code class="type">int</code>) + <a id="id-1.11.7.37.5.3.1.1.3" class="indexterm"></a> + </span></dt><dd><p> + This is the interval between updates to <code class="literal">autoprewarm.blocks</code>. + The default is 300 seconds. If set to 0, the file will not be + dumped at regular intervals, but only when the server is shut down. + </p></dd></dl></div><p> + These parameters must be set in <code class="filename">postgresql.conf</code>. + Typical usage might be: + </p><pre class="programlisting"> +# postgresql.conf +shared_preload_libraries = 'pg_prewarm' + +pg_prewarm.autoprewarm = true +pg_prewarm.autoprewarm_interval = 300s + +</pre></div><div class="sect2" id="id-1.11.7.37.6"><div class="titlepage"><div><div><h3 class="title">F.28.3. Author</h3></div></div></div><p> + Robert Haas <code class="email"><<a class="email" href="mailto:rhaas@postgresql.org">rhaas@postgresql.org</a>></code> + </p></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgfreespacemap.html" title="F.27. pg_freespacemap">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="pgrowlocks.html" title="F.29. pgrowlocks">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.27. pg_freespacemap </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.29. pgrowlocks</td></tr></table></div></body></html>
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