diff options
Diffstat (limited to 'www/c3ref/wal_checkpoint_v2.html')
-rw-r--r-- | www/c3ref/wal_checkpoint_v2.html | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/www/c3ref/wal_checkpoint_v2.html b/www/c3ref/wal_checkpoint_v2.html new file mode 100644 index 0000000..bbd2e61 --- /dev/null +++ b/www/c3ref/wal_checkpoint_v2.html @@ -0,0 +1,224 @@ +<!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>Checkpoint a database</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_wal_checkpoint_v2 --> +<div class=nosearch> +<a href="intro.html"><h2>SQLite C Interface</h2></a> +<h2>Checkpoint a database</h2> +</div> +<blockquote><pre> +int sqlite3_wal_checkpoint_v2( + sqlite3 *db, /* Database handle */ + const char *zDb, /* Name of attached database (or NULL) */ + int eMode, /* SQLITE_CHECKPOINT_* value */ + int *pnLog, /* OUT: Size of WAL log in frames */ + int *pnCkpt /* OUT: Total number of frames checkpointed */ +); +</pre></blockquote> +<p> +The sqlite3_wal_checkpoint_v2(D,X,M,L,C) interface runs a checkpoint +operation on database X of <a href="../c3ref/sqlite3.html">database connection</a> D in mode M. Status +information is written back into integers pointed to by L and C. +The M parameter must be a valid <a href="../c3ref/c_checkpoint_full.html">checkpoint mode</a>:</p> + +<p><dl> +<dt>SQLITE_CHECKPOINT_PASSIVE<dd> +Checkpoint as many frames as possible without waiting for any database +readers or writers to finish, then sync the database file if all frames +in the log were checkpointed. The <a href="../c3ref/busy_handler.html">busy-handler callback</a> +is never invoked in the SQLITE_CHECKPOINT_PASSIVE mode. +On the other hand, passive mode might leave the checkpoint unfinished +if there are concurrent readers or writers.</p> + +<p><dt>SQLITE_CHECKPOINT_FULL<dd> +This mode blocks (it invokes the +<a href="../c3ref/busy_handler.html">busy-handler callback</a>) until there is no +database writer and all readers are reading from the most recent database +snapshot. It then checkpoints all frames in the log file and syncs the +database file. This mode blocks new database writers while it is pending, +but new database readers are allowed to continue unimpeded.</p> + +<p><dt>SQLITE_CHECKPOINT_RESTART<dd> +This mode works the same way as SQLITE_CHECKPOINT_FULL with the addition +that after checkpointing the log file it blocks (calls the +<a href="../c3ref/busy_handler.html">busy-handler callback</a>) +until all readers are reading from the database file only. This ensures +that the next writer will restart the log file from the beginning. +Like SQLITE_CHECKPOINT_FULL, this mode blocks new +database writer attempts while it is pending, but does not impede readers.</p> + +<p><dt>SQLITE_CHECKPOINT_TRUNCATE<dd> +This mode works the same way as SQLITE_CHECKPOINT_RESTART with the +addition that it also truncates the log file to zero bytes just prior +to a successful return. +</dl></p> + +<p>If pnLog is not NULL, then *pnLog is set to the total number of frames in +the log file or to -1 if the checkpoint could not run because +of an error or because the database is not in <a href="../wal.html">WAL mode</a>. If pnCkpt is not +NULL,then *pnCkpt is set to the total number of checkpointed frames in the +log file (including any that were already checkpointed before the function +was called) or to -1 if the checkpoint could not run due to an error or +because the database is not in WAL mode. Note that upon successful +completion of an SQLITE_CHECKPOINT_TRUNCATE, the log file will have been +truncated to zero bytes and so both *pnLog and *pnCkpt will be set to zero.</p> + +<p>All calls obtain an exclusive "checkpoint" lock on the database file. If +any other process is running a checkpoint operation at the same time, the +lock cannot be obtained and SQLITE_BUSY is returned. Even if there is a +busy-handler configured, it will not be invoked in this case.</p> + +<p>The SQLITE_CHECKPOINT_FULL, RESTART and TRUNCATE modes also obtain the +exclusive "writer" lock on the database file. If the writer lock cannot be +obtained immediately, and a busy-handler is configured, it is invoked and +the writer lock retried until either the busy-handler returns 0 or the lock +is successfully obtained. The busy-handler is also invoked while waiting for +database readers as described above. If the busy-handler returns 0 before +the writer lock is obtained or while waiting for database readers, the +checkpoint operation proceeds from that point in the same way as +SQLITE_CHECKPOINT_PASSIVE - checkpointing as many frames as possible +without blocking any further. SQLITE_BUSY is returned in this case.</p> + +<p>If parameter zDb is NULL or points to a zero length string, then the +specified operation is attempted on all WAL databases <a href="../lang_attach.html">attached</a> to +<a href="../c3ref/sqlite3.html">database connection</a> db. In this case the +values written to output parameters *pnLog and *pnCkpt are undefined. If +an SQLITE_BUSY error is encountered when processing one or more of the +attached WAL databases, the operation is still attempted on any remaining +attached databases and SQLITE_BUSY is returned at the end. If any other +error occurs while processing an attached database, processing is abandoned +and the error code is returned to the caller immediately. If no error +(SQLITE_BUSY or otherwise) is encountered while processing the attached +databases, SQLITE_OK is returned.</p> + +<p>If database zDb is the name of an attached database that is not in WAL +mode, SQLITE_OK is returned and both *pnLog and *pnCkpt set to -1. If +zDb is not NULL (or a zero length string) and is not the name of any +attached database, SQLITE_ERROR is returned to the caller.</p> + +<p>Unless it returns SQLITE_MISUSE, +the sqlite3_wal_checkpoint_v2() interface +sets the error information that is queried by +<a href="../c3ref/errcode.html">sqlite3_errcode()</a> and <a href="../c3ref/errcode.html">sqlite3_errmsg()</a>.</p> + +<p>The <a href="../pragma.html#pragma_wal_checkpoint">PRAGMA wal_checkpoint</a> command can be used to invoke this interface +from SQL. +</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> + |