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diff --git a/www/c3ref/backup_finish.html b/www/c3ref/backup_finish.html new file mode 100644 index 0000000..bdd1acd --- /dev/null +++ b/www/c3ref/backup_finish.html @@ -0,0 +1,327 @@ +<!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>Online Backup API.</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_backup_finish sqlite3_backup_init sqlite3_backup_pagecount sqlite3_backup_remaining sqlite3_backup_step --> +<div class=nosearch> +<a href="../c3ref/intro.html"><h2>SQLite C Interface</h2></a> +<h2>Online Backup API.</h2> +</div> +<blockquote><pre> +sqlite3_backup *sqlite3_backup_init( + sqlite3 *pDest, /* Destination database handle */ + const char *zDestName, /* Destination database name */ + sqlite3 *pSource, /* Source database handle */ + const char *zSourceName /* Source database name */ +); +int sqlite3_backup_step(sqlite3_backup *p, int nPage); +int sqlite3_backup_finish(sqlite3_backup *p); +int sqlite3_backup_remaining(sqlite3_backup *p); +int sqlite3_backup_pagecount(sqlite3_backup *p); +</pre></blockquote> +<p> +The backup API copies the content of one database into another. +It is useful either for creating backups of databases or +for copying in-memory databases to or from persistent files.</p> + +<p>See Also: <a href="../backup.html">Using the SQLite Online Backup API</a></p> + +<p>SQLite holds a write transaction open on the destination database file +for the duration of the backup operation. +The source database is read-locked only while it is being read; +it is not locked continuously for the entire backup operation. +Thus, the backup may be performed on a live source database without +preventing other database connections from +reading or writing to the source database while the backup is underway.</p> + +<p>To perform a backup operation: +<ol> +<li><b>sqlite3_backup_init()</b> is called once to initialize the +backup, +<li><b>sqlite3_backup_step()</b> is called one or more times to transfer +the data between the two databases, and finally +<li><b>sqlite3_backup_finish()</b> is called to release all resources +associated with the backup operation. +</ol> +There should be exactly one call to sqlite3_backup_finish() for each +successful call to sqlite3_backup_init().</p> + +<p><a name="sqlite3backupinit"></a> + <b>sqlite3_backup_init()</b></p> + +<p>The D and N arguments to sqlite3_backup_init(D,N,S,M) are the +<a href="../c3ref/sqlite3.html">database connection</a> associated with the destination database +and the database name, respectively. +The database name is "main" for the main database, "temp" for the +temporary database, or the name specified after the AS keyword in +an <a href="../lang_attach.html">ATTACH</a> statement for an attached database. +The S and M arguments passed to +sqlite3_backup_init(D,N,S,M) identify the <a href="../c3ref/sqlite3.html">database connection</a> +and database name of the source database, respectively. +The source and destination <a href="../c3ref/sqlite3.html">database connections</a> (parameters S and D) +must be different or else sqlite3_backup_init(D,N,S,M) will fail with +an error.</p> + +<p>A call to sqlite3_backup_init() will fail, returning NULL, if +there is already a read or read-write transaction open on the +destination database.</p> + +<p>If an error occurs within sqlite3_backup_init(D,N,S,M), then NULL is +returned and an error code and error message are stored in the +destination <a href="../c3ref/sqlite3.html">database connection</a> D. +The error code and message for the failed call to sqlite3_backup_init() +can be retrieved using the <a href="../c3ref/errcode.html">sqlite3_errcode()</a>, <a href="../c3ref/errcode.html">sqlite3_errmsg()</a>, and/or +<a href="../c3ref/errcode.html">sqlite3_errmsg16()</a> functions. +A successful call to sqlite3_backup_init() returns a pointer to an +<a href="../c3ref/backup.html">sqlite3_backup</a> object. +The <a href="../c3ref/backup.html">sqlite3_backup</a> object may be used with the sqlite3_backup_step() and +sqlite3_backup_finish() functions to perform the specified backup +operation.</p> + +<p><a name="sqlite3backupstep"></a> + <b>sqlite3_backup_step()</b></p> + +<p>Function sqlite3_backup_step(B,N) will copy up to N pages between +the source and destination databases specified by <a href="../c3ref/backup.html">sqlite3_backup</a> object B. +If N is negative, all remaining source pages are copied. +If sqlite3_backup_step(B,N) successfully copies N pages and there +are still more pages to be copied, then the function returns <a href="../rescode.html#ok">SQLITE_OK</a>. +If sqlite3_backup_step(B,N) successfully finishes copying all pages +from source to destination, then it returns <a href="../rescode.html#done">SQLITE_DONE</a>. +If an error occurs while running sqlite3_backup_step(B,N), +then an <a href="../rescode.html">error code</a> is returned. As well as <a href="../rescode.html#ok">SQLITE_OK</a> and +<a href="../rescode.html#done">SQLITE_DONE</a>, a call to sqlite3_backup_step() may return <a href="../rescode.html#readonly">SQLITE_READONLY</a>, +<a href="../rescode.html#nomem">SQLITE_NOMEM</a>, <a href="../rescode.html#busy">SQLITE_BUSY</a>, <a href="../rescode.html#locked">SQLITE_LOCKED</a>, or an +<a href="../rescode.html#ioerr_access">SQLITE_IOERR_XXX</a> extended error code.</p> + +<p>The sqlite3_backup_step() might return <a href="../rescode.html#readonly">SQLITE_READONLY</a> if +<ol> +<li> the destination database was opened read-only, or +<li> the destination database is using write-ahead-log journaling +and the destination and source page sizes differ, or +<li> the destination database is an in-memory database and the +destination and source page sizes differ. +</ol></p> + +<p>If sqlite3_backup_step() cannot obtain a required file-system lock, then +the <a href="../c3ref/busy_handler.html">busy-handler function</a> +is invoked (if one is specified). If the +busy-handler returns non-zero before the lock is available, then +<a href="../rescode.html#busy">SQLITE_BUSY</a> is returned to the caller. In this case the call to +sqlite3_backup_step() can be retried later. If the source +<a href="../c3ref/sqlite3.html">database connection</a> +is being used to write to the source database when sqlite3_backup_step() +is called, then <a href="../rescode.html#locked">SQLITE_LOCKED</a> is returned immediately. Again, in this +case the call to sqlite3_backup_step() can be retried later on. If +<a href="../rescode.html#ioerr_access">SQLITE_IOERR_XXX</a>, <a href="../rescode.html#nomem">SQLITE_NOMEM</a>, or +<a href="../rescode.html#readonly">SQLITE_READONLY</a> is returned, then +there is no point in retrying the call to sqlite3_backup_step(). These +errors are considered fatal. The application must accept +that the backup operation has failed and pass the backup operation handle +to the sqlite3_backup_finish() to release associated resources.</p> + +<p>The first call to sqlite3_backup_step() obtains an exclusive lock +on the destination file. The exclusive lock is not released until either +sqlite3_backup_finish() is called or the backup operation is complete +and sqlite3_backup_step() returns <a href="../rescode.html#done">SQLITE_DONE</a>. Every call to +sqlite3_backup_step() obtains a <a href="../lockingv3.html#shared_lock">shared lock</a> on the source database that +lasts for the duration of the sqlite3_backup_step() call. +Because the source database is not locked between calls to +sqlite3_backup_step(), the source database may be modified mid-way +through the backup process. If the source database is modified by an +external process or via a database connection other than the one being +used by the backup operation, then the backup will be automatically +restarted by the next call to sqlite3_backup_step(). If the source +database is modified by the using the same database connection as is used +by the backup operation, then the backup database is automatically +updated at the same time.</p> + +<p><a name="sqlite3backupfinish"></a> + <b>sqlite3_backup_finish()</b></p> + +<p>When sqlite3_backup_step() has returned <a href="../rescode.html#done">SQLITE_DONE</a>, or when the +application wishes to abandon the backup operation, the application +should destroy the <a href="../c3ref/backup.html">sqlite3_backup</a> by passing it to sqlite3_backup_finish(). +The sqlite3_backup_finish() interfaces releases all +resources associated with the <a href="../c3ref/backup.html">sqlite3_backup</a> object. +If sqlite3_backup_step() has not yet returned <a href="../rescode.html#done">SQLITE_DONE</a>, then any +active write-transaction on the destination database is rolled back. +The <a href="../c3ref/backup.html">sqlite3_backup</a> object is invalid +and may not be used following a call to sqlite3_backup_finish().</p> + +<p>The value returned by sqlite3_backup_finish is <a href="../rescode.html#ok">SQLITE_OK</a> if no +sqlite3_backup_step() errors occurred, regardless or whether or not +sqlite3_backup_step() completed. +If an out-of-memory condition or IO error occurred during any prior +sqlite3_backup_step() call on the same <a href="../c3ref/backup.html">sqlite3_backup</a> object, then +sqlite3_backup_finish() returns the corresponding <a href="../rescode.html">error code</a>.</p> + +<p>A return of <a href="../rescode.html#busy">SQLITE_BUSY</a> or <a href="../rescode.html#locked">SQLITE_LOCKED</a> from sqlite3_backup_step() +is not a permanent error and does not affect the return value of +sqlite3_backup_finish().</p> + +<p><a name="sqlite3backupremaining"></a> + <a name="sqlite3backuppagecount"></a> + +<b>sqlite3_backup_remaining() and sqlite3_backup_pagecount()</b></p> + +<p>The sqlite3_backup_remaining() routine returns the number of pages still +to be backed up at the conclusion of the most recent sqlite3_backup_step(). +The sqlite3_backup_pagecount() routine returns the total number of pages +in the source database at the conclusion of the most recent +sqlite3_backup_step(). +The values returned by these functions are only updated by +sqlite3_backup_step(). If the source database is modified in a way that +changes the size of the source database or the number of pages remaining, +those changes are not reflected in the output of sqlite3_backup_pagecount() +and sqlite3_backup_remaining() until after the next +sqlite3_backup_step().</p> + +<p><b>Concurrent Usage of Database Handles</b></p> + +<p>The source <a href="../c3ref/sqlite3.html">database connection</a> may be used by the application for other +purposes while a backup operation is underway or being initialized. +If SQLite is compiled and configured to support threadsafe database +connections, then the source database connection may be used concurrently +from within other threads.</p> + +<p>However, the application must guarantee that the destination +<a href="../c3ref/sqlite3.html">database connection</a> is not passed to any other API (by any thread) after +sqlite3_backup_init() is called and before the corresponding call to +sqlite3_backup_finish(). SQLite does not currently check to see +if the application incorrectly accesses the destination <a href="../c3ref/sqlite3.html">database connection</a> +and so no error code is reported, but the operations may malfunction +nevertheless. Use of the destination database connection while a +backup is in progress might also cause a mutex deadlock.</p> + +<p>If running in <a href="../sharedcache.html">shared cache mode</a>, the application must +guarantee that the shared cache used by the destination database +is not accessed while the backup is running. In practice this means +that the application must guarantee that the disk file being +backed up to is not accessed by any connection within the process, +not just the specific connection that was passed to sqlite3_backup_init().</p> + +<p>The <a href="../c3ref/backup.html">sqlite3_backup</a> object itself is partially threadsafe. Multiple +threads may safely make multiple concurrent calls to sqlite3_backup_step(). +However, the sqlite3_backup_remaining() and sqlite3_backup_pagecount() +APIs are not strictly speaking threadsafe. If they are invoked at the +same time as another thread is invoking sqlite3_backup_step() it is +possible that they return invalid values. +</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> + |