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diff --git a/www/memstat.html b/www/memstat.html new file mode 100644 index 0000000..e209961 --- /dev/null +++ b/www/memstat.html @@ -0,0 +1,203 @@ +<!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>The SQLITE_MEMSTAT Virtual Table</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> +<div class=fancy> +<div class=nosearch> +<div class="fancy_title"> +The SQLITE_MEMSTAT Virtual Table +</div> +</div> + + + + +<h1 id="overview"><span>1. </span>Overview</h1> + +<p> +The SQLITE_MEMSTAT extension implements an <a href="vtab.html#epoonlyvtab">eponymous-only virtual table</a> that +provides SQL access to the <a href="c3ref/status.html">sqlite3_status64()</a> and +<a href="c3ref/db_status.html">sqlite3_db_status()</a> interfaces. +</p> + +<p> +The SQLITE_STMT extension can also be loaded at run-time +by compiling the extension into a shared library or DLL using the source +code at <a href="https://sqlite.org/src/file/ext/misc/memstat.c">https://sqlite.org/src/file/ext/misc/memstat.c</a> and following the +instructions for how to <a href="loadext.html#build">compile loadable extensions</a>. +</p> + +<h1 id="usage"><span>2. </span>Usage</h1> + +<p> +The SQLITE_MEMSTAT virtual table is a read-only table that can be +queried to determine performance characteristics (primarily the +amount of memory being used) of the current instance of SQLite. +The SQLITE_MEMSTATE table is essentially a wrapper around the +C-language APIs <a href="c3ref/status.html">sqlite3_status64()</a> and <a href="c3ref/db_status.html">sqlite3_db_status()</a>. +If the +<a href="https://sqlite.org/src/file/ext/misc/memstat.c">memstat.c</a> source +file is compiled with the -DSQLITE_ENABLE_ZIPVFS option, then SQLITE_MEMSTAT +will also do some <a href="c3ref/file_control.html">file-control</a> calls to extract +memory usage information about the +<a href="https://www.hwaci.com/sw/sqlite/zipvfs.html">ZIPVFS</a> subsystem, +if that subsystem as been licensed, installed, and is in use. + +</p><p> +The SQLITE_MEMSTAT table appears to have the following schema: + +</p><div class="codeblock"><pre>CREATE TABLE sqlite_memstat( + name TEXT, + schema TEXT, + value INT, + hiwtr INT +); +</pre></div> + +<p> +Each row of the SQLITE_MEMSTAT table corresponds to a single call to +one of the <a href="c3ref/status.html">sqlite3_status64()</a> or <a href="c3ref/db_status.html">sqlite3_db_status()</a> interfaces. +The NAME column of the row identifies which "verb" was passed to those +interfaces. For example, if <a href="c3ref/status.html">sqlite3_status64()</a> is invoked with +<a href="c3ref/c_status_malloc_count.html#sqlitestatusmemoryused">SQLITE_STATUS_MEMORY_USED</a>, then the NAME column is 'MEMORY_USED'. +Or if <a href="c3ref/db_status.html">sqlite3_db_status()</a> is invoked with <a href="c3ref/c_dbstatus_options.html#sqlitedbstatuscacheused">SQLITE_DBSTATUS_CACHE_USED</a>, +then the NAME column is "DB_CACHE_USED". + +</p><p> +The SCHEMA column is NULL, except for cases when the <a href="c3ref/file_control.html">sqlite3_file_control()</a> +interface is used to interrogate the ZIPVFS backend. As this only happens +when the memstat.c module is compiled with -DSQLITE_ENABLE_ZIPVFS and when +<a href="https://www.hwaci.com/sw/sqlite/zipvfs.html">ZIPVFS</a> is in use, +SCHEMA is usually NULL. + +</p><p> +The VALUE and HIWTR columns report the current value of the measure and +its "high-water mark". The high-water mark is the highest value ever seen +for the measurement, at least since the last reset. The SQLITE_MEMSTAT +virtual table does not provide a mechanism for resetting the high-water mark. + +</p><p> +Depending on which parameter is being interrogated, one of the VALUE +or HIWTR mark measurements might be undefined. For example, only the +high-water mark is meaningful for <a href="c3ref/c_status_malloc_count.html#sqlitestatusmallocsize">SQLITE_STATUS_MALLOC_SIZE</a>, and +only the current value is meaningful for <a href="c3ref/c_dbstatus_options.html#sqlitedbstatuscacheused">SQLITE_DBSTATUS_CACHE_USED</a>. +For rows where one or the other of VALUE or HIWTR is not meaningful, +that value is returned as NULL. +the + +interfaces, with the initial +</p><p align="center"><small><i>This page last modified on <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink" data-href="https://sqlite.org/docsrc/finfo/pages/memstat.in?m=4d88e885eb">2022-01-08 05:02:57</a> UTC </small></i></p> + |