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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Run-time Limits</title><style type="text/css">body { margin: auto; font-family: "Verdana" "sans-serif"; padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline { float:right; text-align:right; font-style:italic; width:240px; margin:12px; margin-top:58px;}.toolbar { font-variant: small-caps; text-align: center; line-height: 1.6em; margin: 0; padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se { background: url(../images/se.png) 100% 100% no-repeat #80a796}.sw { background: url(../images/sw.png) 0% 100% no-repeat }.ne { background: url(../images/ne.png) 100% 0% no-repeat }.nw { background: url(../images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head><body><div><!-- container div to satisfy validator --><a href="../index.html"><img class="logo" src="../images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. Fast. Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td> <div class="se"><div class="sw"><div class="ne"><div class="nw"> <div class="toolbar"> <a href="../about.html">About</a> <a href="../sitemap.html">Sitemap</a> <a href="../docs.html">Documentation</a> <a href="../download.html">Download</a> <a href="../copyright.html">License</a> <a href="../news.html">News</a> <a href="http://www.sqlite.org/cvstrac/index">Developers</a> <a href="../support.html">Support</a> </div></div></div></div></div></td></tr></table> <a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Run-time Limits</h2><blockquote><pre>int sqlite3_limit(sqlite3*, int id, int newVal);</pre></blockquote><p>This interface allows the size of various constructs to be limitedon a connection by connection basis. The first parameter is the<a href="../c3ref/sqlite3.html">database connection</a> whose limit is to be set or queried. Thesecond parameter is one of the <a href="../c3ref/c_limit_attached.html">limit categories</a> that define aclass of constructs to be size limited. The third parameter is thenew limit for that construct. The function returns the old limit.</p><p>If the new limit is a negative number, the limit is unchanged.For the limit category of SQLITE_LIMIT_XYZ there is a hard upperbound set by a compile-time C-preprocess macro named SQLITE_MAX_XYZ.(The "_LIMIT_" in the name is changed to "_MAX_".)Attempts to increase a limit above its hard upper bound aresilently truncated to the hard upper limit.</p><p>Run time limits are intended for use in applications that manageboth their own internal database and also databases that are controlledby untrusted external sources. An example application might be awebbrowser that has its own databases for storing history andseparate databases controlled by javascript applications downloadedoff the internet. The internal databases can be given thelarge, default limits. Databases managed by external sources canbe given much smaller limits designed to prevent a denial of serviceattach. Developers might also want to use the <a href="../c3ref/set_authorizer.html">sqlite3_set_authorizer()</a>interface to further control untrusted SQL. The size of the databasecreated by an untrusted script can be contained using the<a href="../pragma.html#pragma_max_page_count">max_page_count</a> <a href="../pragma.html#syntax">PRAGMA</a>.</p><p>This interface is currently considered experimental and is subjectto change or removal without prior notice.</p><p><h3>Invariants:</h3><table border="0" cellpadding="5" cellspacing="0"><tr><td valign="top">F12762</td> <td valign="top">A successful call to <a href="../c3ref/limit.html">sqlite3_limit(D,C,V)</a> where V ispositive changes thelimit on the size of construct C in <a href="../c3ref/sqlite3.html">database connection</a> Dto the lessor of V and the hard upper bound on the sizeof C that is set at compile-time.</td></tr><tr><td valign="top">F12766</td> <td valign="top">A successful call to <a href="../c3ref/limit.html">sqlite3_limit(D,C,V)</a> where V is negativeleaves the state of <a href="../c3ref/sqlite3.html">database connection</a> D unchanged.</td></tr><tr><td valign="top">F12769</td> <td valign="top">A successful call to <a href="../c3ref/limit.html">sqlite3_limit(D,C,V)</a> returns thevalue of the limit on the size of construct C inin <a href="../c3ref/sqlite3.html">database connection</a> D as it was prior to the call.</td></tr></table></p><p>See also lists of <a href="objlist.html">Objects</a>, <a href="constlist.html">Constants</a>, and <a href="funclist.html">Functions</a>.</p><hr><small><i>This page last modified 2008/05/12 13:08:44 UTC</i></small></div></body></html>⌨️ 快捷键说明
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