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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Query Progress Callbacks</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>Query Progress Callbacks</h2><blockquote><pre>void sqlite3_progress_handler(sqlite3*, int, int(*)(void*), void*);</pre></blockquote><p>This routine configures a callback function - theprogress callback - that is invoked periodically during longrunning calls to <a href="../c3ref/exec.html">sqlite3_exec()</a>, <a href="../c3ref/step.html">sqlite3_step()</a> and<a href="../c3ref/free_table.html">sqlite3_get_table()</a>. An example use for thisinterface is to keep a GUI updated during a large query.</p><p>If the progress callback returns non-zero, the opertion isinterrupted. This feature can be used to implement a"Cancel" button on a GUI dialog box.</p><p><h3>Invariants:</h3><table border="0" cellpadding="5" cellspacing="0"><tr><td valign="top">F12911</td> <td valign="top">The callback function registered by <a href="../c3ref/progress_handler.html">sqlite3_progress_handler()</a>is invoked periodically during long running calls to<a href="../c3ref/step.html">sqlite3_step()</a>.</td></tr><tr><td valign="top">F12912</td> <td valign="top">The progress callback is invoked once for every N virtualmachine opcodes, where N is the second argument tothe <a href="../c3ref/progress_handler.html">sqlite3_progress_handler()</a> call that registeredthe callback. <font color="red">(TODO: What if N is less than 1?)</font></td></tr><tr><td valign="top">F12913</td> <td valign="top">The progress callback itself is identified by the thirdargument to <a href="../c3ref/progress_handler.html">sqlite3_progress_handler()</a>.</td></tr><tr><td valign="top">F12914</td> <td valign="top">The fourth argument <a href="../c3ref/progress_handler.html">sqlite3_progress_handler()</a> is avoid pointer passed to the progress callbackfunction each time it is invoked.</td></tr><tr><td valign="top">F12915</td> <td valign="top">If a call to <a href="../c3ref/step.html">sqlite3_step()</a> results in fewer thanN opcodes being executed,then the progress callback is never invoked.</td></tr><tr><td valign="top">F12916</td> <td valign="top">Every call to <a href="../c3ref/progress_handler.html">sqlite3_progress_handler()</a>overwrites any previously registere progress handler.</td></tr><tr><td valign="top">F12917</td> <td valign="top">If the progress handler callback is NULL then no progresshandler is invoked.</td></tr><tr><td valign="top">F12918</td> <td valign="top">If the progress callback returns a result other than 0, thenthe behavior is a if <a href="../c3ref/interrupt.html">sqlite3_interrupt()</a> had been called.</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 2008/01/31 20:37:13 UTC</i></small></div></body></html>⌨️ 快捷键说明
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