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diff --git a/doc/src/sgml/html/locking-indexes.html b/doc/src/sgml/html/locking-indexes.html new file mode 100644 index 0000000..b61d1d7 --- /dev/null +++ b/doc/src/sgml/html/locking-indexes.html @@ -0,0 +1,42 @@ +<?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>13.6. Locking and Indexes</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="mvcc-caveats.html" title="13.5. Caveats" /><link rel="next" href="performance-tips.html" title="Chapter 14. Performance Tips" /></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">13.6. Locking and Indexes</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="mvcc-caveats.html" title="13.5. Caveats">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="mvcc.html" title="Chapter 13. Concurrency Control">Up</a></td><th width="60%" align="center">Chapter 13. Concurrency Control</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="performance-tips.html" title="Chapter 14. Performance Tips">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="LOCKING-INDEXES"><div class="titlepage"><div><div><h2 class="title" style="clear: both">13.6. Locking and Indexes</h2></div></div></div><a id="id-1.5.12.9.2" class="indexterm"></a><p> + Though <span class="productname">PostgreSQL</span> + provides nonblocking read/write access to table + data, nonblocking read/write access is not currently offered for every + index access method implemented + in <span class="productname">PostgreSQL</span>. + The various index types are handled as follows: + + </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"> + B-tree, <acronym class="acronym">GiST</acronym> and <acronym class="acronym">SP-GiST</acronym> indexes + </span></dt><dd><p> + Short-term share/exclusive page-level locks are used for + read/write access. Locks are released immediately after each + index row is fetched or inserted. These index types provide + the highest concurrency without deadlock conditions. + </p></dd><dt><span class="term"> + Hash indexes + </span></dt><dd><p> + Share/exclusive hash-bucket-level locks are used for read/write + access. Locks are released after the whole bucket is processed. + Bucket-level locks provide better concurrency than index-level + ones, but deadlock is possible since the locks are held longer + than one index operation. + </p></dd><dt><span class="term"> + <acronym class="acronym">GIN</acronym> indexes + </span></dt><dd><p> + Short-term share/exclusive page-level locks are used for + read/write access. Locks are released immediately after each + index row is fetched or inserted. But note that insertion of a + GIN-indexed value usually produces several index key insertions + per row, so GIN might do substantial work for a single value's + insertion. + </p></dd></dl></div><p> + </p><p> + Currently, B-tree indexes offer the best performance for concurrent + applications; since they also have more features than hash + indexes, they are the recommended index type for concurrent + applications that need to index scalar data. When dealing with + non-scalar data, B-trees are not useful, and GiST, SP-GiST or GIN + indexes should be used instead. + </p></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="mvcc-caveats.html" title="13.5. Caveats">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="mvcc.html" title="Chapter 13. Concurrency Control">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="performance-tips.html" title="Chapter 14. Performance Tips">Next</a></td></tr><tr><td width="40%" align="left" valign="top">13.5. Caveats </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"> Chapter 14. Performance Tips</td></tr></table></div></body></html>
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