189 lines
6.6 KiB
HTML
189 lines
6.6 KiB
HTML
<!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>Autovacuum Compaction Amount Callback</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>
|
|
<li class='desktoponly'><a href="../docs.html">Documentation</a>
|
|
<li class='desktoponly'><a href="../download.html">Download</a>
|
|
<li class='wideonly'><a href='../copyright.html'>License</a>
|
|
<li class='desktoponly'><a href="../support.html">Support</a>
|
|
<li class='desktoponly'><a href="../prosupport.html">Purchase</a>
|
|
<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>
|
|
<option value="c">Search Changelog</option>
|
|
</select>
|
|
<input type="text" name="q" id="searchbox" value="">
|
|
<input type="submit" value="Go">
|
|
</form>
|
|
</div>
|
|
</div>
|
|
<script>
|
|
function toggle_div(nm) {
|
|
var w = document.getElementById(nm);
|
|
if( w.style.display=="block" ){
|
|
w.style.display = "none";
|
|
}else{
|
|
w.style.display = "block";
|
|
}
|
|
}
|
|
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);
|
|
}
|
|
}
|
|
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);
|
|
var b = document.getElementById(btn);
|
|
if( x.style.display!='none' ){
|
|
x.style.display = 'none';
|
|
b.innerHTML='show';
|
|
}else{
|
|
x.style.display = '';
|
|
b.innerHTML='hide';
|
|
}
|
|
return false;
|
|
}
|
|
var antiRobot = 0;
|
|
function antiRobotGo(){
|
|
if( antiRobot!=3 ) return;
|
|
antiRobot = 7;
|
|
var j = document.getElementById("mtimelink");
|
|
if(j && j.hasAttribute("data-href")) j.href=j.getAttribute("data-href");
|
|
}
|
|
function antiRobotDefense(){
|
|
document.body.onmousedown=function(){
|
|
antiRobot |= 2;
|
|
antiRobotGo();
|
|
document.body.onmousedown=null;
|
|
}
|
|
document.body.onmousemove=function(){
|
|
antiRobot |= 2;
|
|
antiRobotGo();
|
|
document.body.onmousemove=null;
|
|
}
|
|
setTimeout(function(){
|
|
antiRobot |= 1;
|
|
antiRobotGo();
|
|
}, 100)
|
|
antiRobotGo();
|
|
}
|
|
antiRobotDefense();
|
|
</script>
|
|
<!-- keywords: sqlite3_autovacuum_pages -->
|
|
<div class=nosearch>
|
|
<a href="../c3ref/intro.html"><h2>SQLite C Interface</h2></a>
|
|
<h2>Autovacuum Compaction Amount Callback</h2>
|
|
</div>
|
|
<blockquote><pre>
|
|
int sqlite3_autovacuum_pages(
|
|
sqlite3 *db,
|
|
unsigned int(*)(void*,const char*,unsigned int,unsigned int,unsigned int),
|
|
void*,
|
|
void(*)(void*)
|
|
);
|
|
</pre></blockquote>
|
|
<p>
|
|
The sqlite3_autovacuum_pages(D,C,P,X) interface registers a callback
|
|
function C that is invoked prior to each autovacuum of the database
|
|
file. The callback is passed a copy of the generic data pointer (P),
|
|
the schema-name of the attached database that is being autovacuumed,
|
|
the size of the database file in pages, the number of free pages,
|
|
and the number of bytes per page, respectively. The callback should
|
|
return the number of free pages that should be removed by the
|
|
autovacuum. If the callback returns zero, then no autovacuum happens.
|
|
If the value returned is greater than or equal to the number of
|
|
free pages, then a complete autovacuum happens.</p>
|
|
|
|
<p><p>If there are multiple ATTACH-ed database files that are being
|
|
modified as part of a transaction commit, then the autovacuum pages
|
|
callback is invoked separately for each file.</p>
|
|
|
|
<p><p><b>The callback is not reentrant.</b> The callback function should
|
|
not attempt to invoke any other SQLite interface. If it does, bad
|
|
things may happen, including segmentation faults and corrupt database
|
|
files. The callback function should be a simple function that
|
|
does some arithmetic on its input parameters and returns a result.</p>
|
|
|
|
<p>The X parameter to sqlite3_autovacuum_pages(D,C,P,X) is an optional
|
|
destructor for the P parameter. If X is not NULL, then X(P) is
|
|
invoked whenever the database connection closes or when the callback
|
|
is overwritten by another invocation of sqlite3_autovacuum_pages().</p>
|
|
|
|
<p><p>There is only one autovacuum pages callback per database connection.
|
|
Each call to the sqlite3_autovacuum_pages() interface overrides all
|
|
previous invocations for that database connection. If the callback
|
|
argument (C) to sqlite3_autovacuum_pages(D,C,P,X) is a NULL pointer,
|
|
then the autovacuum steps callback is canceled. The return value
|
|
from sqlite3_autovacuum_pages() is normally SQLITE_OK, but might
|
|
be some other error code if something goes wrong. The current
|
|
implementation will only return SQLITE_OK or SQLITE_MISUSE, but other
|
|
return codes might be added in future releases.</p>
|
|
|
|
<p><p>If no autovacuum pages callback is specified (the usual case) or
|
|
a NULL pointer is provided for the callback,
|
|
then the default behavior is to vacuum all free pages. So, in other
|
|
words, the default behavior is the same as if the callback function
|
|
were something like this:</p>
|
|
|
|
<p><blockquote><pre>
|
|
unsigned int demonstration_autovac_pages_callback(
|
|
void *pClientData,
|
|
const char *zSchema,
|
|
unsigned int nDbPage,
|
|
unsigned int nFreePage,
|
|
unsigned int nBytePerPage
|
|
){
|
|
return nFreePage;
|
|
}
|
|
</pre></blockquote>
|
|
</p><p>See also lists of
|
|
<a href="../c3ref/objlist.html">Objects</a>,
|
|
<a href="../c3ref/constlist.html">Constants</a>, and
|
|
<a href="../c3ref/funclist.html">Functions</a>.</p>
|
|
|