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<?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>Chapter 13. Concurrency Control</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="[email protected]" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="textsearch-limitations.html" title="12.11. Limitations" /><link rel="next" href="mvcc-intro.html" title="13.1. Introduction" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Chapter 13. Concurrency Control</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="textsearch-limitations.html" title="12.11. Limitations">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql.html" title="Part II. The SQL Language">Up</a></td><th width="60%" align="center">Part II. The SQL Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 10.23 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="mvcc-intro.html" title="13.1. Introduction">Next</a></td></tr></table><hr></hr></div><div class="chapter" id="MVCC"><div class="titlepage"><div><div><h2 class="title">Chapter 13. Concurrency Control</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="mvcc-intro.html">13.1. Introduction</a></span></dt><dt><span class="sect1"><a href="transaction-iso.html">13.2. Transaction Isolation</a></span></dt><dd><dl><dt><span class="sect2"><a href="transaction-iso.html#XACT-READ-COMMITTED">13.2.1. Read Committed Isolation Level</a></span></dt><dt><span class="sect2"><a href="transaction-iso.html#XACT-REPEATABLE-READ">13.2.2. Repeatable Read Isolation Level</a></span></dt><dt><span class="sect2"><a href="transaction-iso.html#XACT-SERIALIZABLE">13.2.3. Serializable Isolation Level</a></span></dt></dl></dd><dt><span class="sect1"><a href="explicit-locking.html">13.3. Explicit Locking</a></span></dt><dd><dl><dt><span class="sect2"><a href="explicit-locking.html#LOCKING-TABLES">13.3.1. Table-level Locks</a></span></dt><dt><span class="sect2"><a href="explicit-locking.html#LOCKING-ROWS">13.3.2. Row-level Locks</a></span></dt><dt><span class="sect2"><a href="explicit-locking.html#LOCKING-PAGES">13.3.3. Page-level Locks</a></span></dt><dt><span class="sect2"><a href="explicit-locking.html#LOCKING-DEADLOCKS">13.3.4. Deadlocks</a></span></dt><dt><span class="sect2"><a href="explicit-locking.html#ADVISORY-LOCKS">13.3.5. Advisory Locks</a></span></dt></dl></dd><dt><span class="sect1"><a href="applevel-consistency.html">13.4. Data Consistency Checks at the Application Level</a></span></dt><dd><dl><dt><span class="sect2"><a href="applevel-consistency.html#SERIALIZABLE-CONSISTENCY">13.4.1. Enforcing Consistency With Serializable Transactions</a></span></dt><dt><span class="sect2"><a href="applevel-consistency.html#NON-SERIALIZABLE-CONSISTENCY">13.4.2. Enforcing Consistency With Explicit Blocking Locks</a></span></dt></dl></dd><dt><span class="sect1"><a href="mvcc-caveats.html">13.5. Caveats</a></span></dt><dt><span class="sect1"><a href="locking-indexes.html">13.6. Locking and Indexes</a></span></dt></dl></div><a id="id-1.5.12.2" class="indexterm"></a><p> This chapter describes the behavior of the <span class="productname">PostgreSQL</span> database system when two or more sessions try to access the same data at the same time. The goals in that situation are to allow efficient access for all sessions while maintaining strict data integrity. Every developer of database applications should be familiar with the topics covered in this chapter. </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="textsearch-limitations.html" title="12.11. Limitations">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql.html" title="Part II. The SQL Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="mvcc-intro.html" title="13.1. Introduction">Next</a></td></tr><tr><td width="40%" align="left" valign="top">12.11. Limitations </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 10.23 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 13.1. Introduction</td></tr></table></div></body></html>