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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-05 17:28:19 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-05 17:28:19 +0000
commit18657a960e125336f704ea058e25c27bd3900dcb (patch)
tree17b438b680ed45a996d7b59951e6aa34023783f2 /www/c3ref/get_auxdata.html
parentInitial commit. (diff)
downloadsqlite3-18657a960e125336f704ea058e25c27bd3900dcb.tar.xz
sqlite3-18657a960e125336f704ea058e25c27bd3900dcb.zip
Adding upstream version 3.40.1.upstream/3.40.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<!DOCTYPE html>
+<html><head>
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<link href="../sqlite.css" rel="stylesheet">
+<title>Function Auxiliary Data</title>
+<!-- path=../ -->
+</head>
+<body>
+<div class=nosearch>
+<a href="../index.html">
+<img class="logo" src="../images/sqlite370_banner.gif" alt="SQLite" border="0">
+</a>
+<div><!-- IE hack to prevent disappearing logo --></div>
+<div class="tagline desktoponly">
+Small. Fast. Reliable.<br>Choose any three.
+</div>
+<div class="menu mainmenu">
+<ul>
+<li><a href="../index.html">Home</a>
+<li class='mobileonly'><a href="javascript:void(0)" onclick='toggle_div("submenu")'>Menu</a>
+<li class='wideonly'><a href='../about.html'>About</a>
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+<li class='desktoponly'><a href="../download.html">Download</a>
+<li class='wideonly'><a href='../copyright.html'>License</a>
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+<li class='search' id='search_menubutton'>
+<a href="javascript:void(0)" onclick='toggle_search()'>Search</a>
+</ul>
+</div>
+<div class="menu submenu" id="submenu">
+<ul>
+<li><a href='../about.html'>About</a>
+<li><a href='../docs.html'>Documentation</a>
+<li><a href='../download.html'>Download</a>
+<li><a href='../support.html'>Support</a>
+<li><a href='../prosupport.html'>Purchase</a>
+</ul>
+</div>
+<div class="searchmenu" id="searchmenu">
+<form method="GET" action="../search">
+<select name="s" id="searchtype">
+<option value="d">Search Documentation</option>
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+</select>
+<input type="text" name="q" id="searchbox" value="">
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+</div>
+<script>
+function toggle_div(nm) {
+var w = document.getElementById(nm);
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+w.style.display = "none";
+}else{
+w.style.display = "block";
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+}
+function toggle_search() {
+var w = document.getElementById("searchmenu");
+if( w.style.display=="block" ){
+w.style.display = "none";
+} else {
+w.style.display = "block";
+setTimeout(function(){
+document.getElementById("searchbox").focus()
+}, 30);
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+function div_off(nm){document.getElementById(nm).style.display="none";}
+window.onbeforeunload = function(e){div_off("submenu");}
+/* Disable the Search feature if we are not operating from CGI, since */
+/* Search is accomplished using CGI and will not work without it. */
+if( !location.origin || !location.origin.match || !location.origin.match(/http/) ){
+document.getElementById("search_menubutton").style.display = "none";
+}
+/* Used by the Hide/Show button beside syntax diagrams, to toggle the */
+function hideorshow(btn,obj){
+var x = document.getElementById(obj);
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+if( x.style.display!='none' ){
+x.style.display = 'none';
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+</script>
+<!-- keywords: sqlite3_get_auxdata sqlite3_set_auxdata -->
+<div class=nosearch>
+<a href="intro.html"><h2>SQLite C Interface</h2></a>
+<h2>Function Auxiliary Data</h2>
+</div>
+<blockquote><pre>
+void *sqlite3_get_auxdata(sqlite3_context*, int N);
+void sqlite3_set_auxdata(sqlite3_context*, int N, void*, void (*)(void*));
+</pre></blockquote>
+<p>
+These functions may be used by (non-aggregate) SQL functions to
+associate metadata with argument values. If the same value is passed to
+multiple invocations of the same SQL function during query execution, under
+some circumstances the associated metadata may be preserved. An example
+of where this might be useful is in a regular-expression matching
+function. The compiled version of the regular expression can be stored as
+metadata associated with the pattern string.
+Then as long as the pattern string remains the same,
+the compiled regular expression can be reused on multiple
+invocations of the same function.</p>
+
+<p>The sqlite3_get_auxdata(C,N) interface returns a pointer to the metadata
+associated by the sqlite3_set_auxdata(C,N,P,X) function with the Nth argument
+value to the application-defined function. N is zero for the left-most
+function argument. If there is no metadata
+associated with the function argument, the sqlite3_get_auxdata(C,N) interface
+returns a NULL pointer.</p>
+
+<p>The sqlite3_set_auxdata(C,N,P,X) interface saves P as metadata for the N-th
+argument of the application-defined function. Subsequent
+calls to sqlite3_get_auxdata(C,N) return P from the most recent
+sqlite3_set_auxdata(C,N,P,X) call if the metadata is still valid or
+NULL if the metadata has been discarded.
+After each call to sqlite3_set_auxdata(C,N,P,X) where X is not NULL,
+SQLite will invoke the destructor function X with parameter P exactly
+once, when the metadata is discarded.
+SQLite is free to discard the metadata at any time, including: <ul>
+<li> when the corresponding function parameter changes, or
+<li> when <a href="../c3ref/reset.html">sqlite3_reset()</a> or <a href="../c3ref/finalize.html">sqlite3_finalize()</a> is called for the
+SQL statement, or
+<li> when sqlite3_set_auxdata() is invoked again on the same
+parameter, or
+<li> during the original sqlite3_set_auxdata() call when a memory
+allocation error occurs. </ul></p>
+
+<p>Note the last bullet in particular. The destructor X in
+sqlite3_set_auxdata(C,N,P,X) might be called immediately, before the
+sqlite3_set_auxdata() interface even returns. Hence sqlite3_set_auxdata()
+should be called near the end of the function implementation and the
+function implementation should not make any use of P after
+sqlite3_set_auxdata() has been called.</p>
+
+<p>In practice, metadata is preserved between function calls for
+function parameters that are compile-time constants, including literal
+values and <a href="../lang_expr.html#varparam">parameters</a> and expressions composed from the same.</p>
+
+<p>The value of the N parameter to these interfaces should be non-negative.
+Future enhancements may make use of negative N values to define new
+kinds of function caching behavior.</p>
+
+<p>These routines must be called from the same thread in which
+the SQL function is running.
+</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>
+
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