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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:19:15 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:19:15 +0000 |
| commit | 6eb9c5a5657d1fe77b55cc261450f3538d35a94d (patch) | |
| tree | 657d8194422a5daccecfd42d654b8a245ef7b4c8 /doc/src/sgml/html/pgfreespacemap.html | |
| parent | Initial commit. (diff) | |
| download | postgresql-13-upstream.tar.xz postgresql-13-upstream.zip | |
Adding upstream version 13.4.upstream/13.4upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/src/sgml/html/pgfreespacemap.html')
| -rw-r--r-- | doc/src/sgml/html/pgfreespacemap.html | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/doc/src/sgml/html/pgfreespacemap.html b/doc/src/sgml/html/pgfreespacemap.html new file mode 100644 index 0000000..5661091 --- /dev/null +++ b/doc/src/sgml/html/pgfreespacemap.html @@ -0,0 +1,70 @@ +<?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.26. pg_freespacemap</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 V1.79.1" /><link rel="prev" href="pgcrypto.html" title="F.25. pgcrypto" /><link rel="next" href="pgprewarm.html" title="F.27. pg_prewarm" /></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.26. pg_freespacemap</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgcrypto.html" title="F.25. pgcrypto">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 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pgprewarm.html" title="F.27. pg_prewarm">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="PGFREESPACEMAP"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.26. pg_freespacemap</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="pgfreespacemap.html#id-1.11.7.35.5">F.26.1. Functions</a></span></dt><dt><span class="sect2"><a href="pgfreespacemap.html#id-1.11.7.35.6">F.26.2. Sample Output</a></span></dt><dt><span class="sect2"><a href="pgfreespacemap.html#id-1.11.7.35.7">F.26.3. Author</a></span></dt></dl></div><a id="id-1.11.7.35.2" class="indexterm"></a><p> + The <code class="filename">pg_freespacemap</code> module provides a means for examining the + free space map (FSM). It provides a function called + <code class="function">pg_freespace</code>, or two overloaded functions, to be + precise. The functions show the value recorded in the free space map for + a given page, or for all pages in the relation. + </p><p> + By default use is restricted to superusers and members of the + <code class="literal">pg_stat_scan_tables</code> role. Access may be granted to others + using <code class="command">GRANT</code>. + </p><div class="sect2" id="id-1.11.7.35.5"><div class="titlepage"><div><div><h3 class="title">F.26.1. Functions</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term"> + <code class="function">pg_freespace(rel regclass IN, blkno bigint IN) returns int2</code> + <a id="id-1.11.7.35.5.2.1.1.2" class="indexterm"></a> + </span></dt><dd><p> + Returns the amount of free space on the page of the relation, specified + by <code class="literal">blkno</code>, according to the FSM. + </p></dd><dt><span class="term"> + <code class="function">pg_freespace(rel regclass IN, blkno OUT bigint, avail OUT int2)</code> + </span></dt><dd><p> + Displays the amount of free space on each page of the relation, + according to the FSM. A set of <code class="literal">(blkno bigint, avail int2)</code> + tuples is returned, one tuple for each page in the relation. + </p></dd></dl></div><p> + The values stored in the free space map are not exact. They're rounded + to precision of 1/256th of <code class="symbol">BLCKSZ</code> (32 bytes with default <code class="symbol">BLCKSZ</code>), and + they're not kept fully up-to-date as tuples are inserted and updated. + </p><p> + For indexes, what is tracked is entirely-unused pages, rather than free + space within pages. Therefore, the values are not meaningful, just + whether a page is full or empty. + </p><div class="note"><h3 class="title">Note</h3><p> + The interface was changed in version 8.4, to reflect the new FSM + implementation introduced in the same version. + </p></div></div><div class="sect2" id="id-1.11.7.35.6"><div class="titlepage"><div><div><h3 class="title">F.26.2. Sample Output</h3></div></div></div><pre class="screen"> +postgres=# SELECT * FROM pg_freespace('foo'); + blkno | avail +-------+------- + 0 | 0 + 1 | 0 + 2 | 0 + 3 | 32 + 4 | 704 + 5 | 704 + 6 | 704 + 7 | 1216 + 8 | 704 + 9 | 704 + 10 | 704 + 11 | 704 + 12 | 704 + 13 | 704 + 14 | 704 + 15 | 704 + 16 | 704 + 17 | 704 + 18 | 704 + 19 | 3648 +(20 rows) + +postgres=# SELECT * FROM pg_freespace('foo', 7); + pg_freespace +-------------- + 1216 +(1 row) +</pre></div><div class="sect2" id="id-1.11.7.35.7"><div class="titlepage"><div><div><h3 class="title">F.26.3. Author</h3></div></div></div><p> + Original version by Mark Kirkwood <code class="email"><<a class="email" href="mailto:markir@paradise.net.nz">markir@paradise.net.nz</a>></code>. + Rewritten in version 8.4 to suit new FSM implementation by Heikki + Linnakangas <code class="email"><<a class="email" href="mailto:heikki@enterprisedb.com">heikki@enterprisedb.com</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="pgcrypto.html" title="F.25. pgcrypto">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="pgprewarm.html" title="F.27. pg_prewarm">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.25. pgcrypto </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.27. pg_prewarm</td></tr></table></div></body></html>
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