diff options
Diffstat (limited to 'www/bytecodevtab.html')
| -rw-r--r-- | www/bytecodevtab.html | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/www/bytecodevtab.html b/www/bytecodevtab.html new file mode 100644 index 0000000..621d209 --- /dev/null +++ b/www/bytecodevtab.html @@ -0,0 +1,232 @@ +<!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 Bytecode() And Tables_Used() Table-Valued Functions</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 Bytecode() And Tables_Used() Table-Valued Functions +</div> +</div> + + + + +<h1 id="overview"><span>1. </span>Overview</h1> + +<p> +Bytecode and tables_used are <a href="vtab.html">virtual tables</a> built into SQLite that +access information about <a href="c3ref/stmt.html">prepared statements</a>. +Both bytecode and tables_used operate as <a href="vtab.html#tabfunc2">table-valued functions</a>. +They take a single required argument which is either the text of +an SQL statement, or a pointer to an existing prepared statement. +The bytecode function returns one row of result for each <a href="opcode.html">bytecode</a> +operation in the prepared statement. The tables_used function returns +one row for each persistent btree (either a table or an index) accessed +by the prepared statement. + +</p><h1 id="usage"><span>2. </span>Usage</h1> + +<p> +The bytecode and tables_used tables are only available if SQLite has +been compiled with the <a href="compile.html#enable_bytecode_vtab">-DSQLITE_ENABLE_BYTECODE_VTAB</a> compile-time option. +The <a href="cli.html">CLI</a> has been compiled that way, and so you can use the standard +<a href="cli.html">CLI</a> as a test platform to experiement. + +</p><p> +Both virtual tables are read-only <a href="vtab.html#epoonlyvtab">eponymous-only virtual tables</a>. You use them +by mentioning them directly in the FROM clause of a SELECT statement. +They both require a single argument which is the SQL statement to be +analyzed. For example: + +</p><div class="codeblock"><pre>SELECT * FROM bytecode('SELECT * FROM bytecode(?1)'); +</pre></div> + +<p> +The argument can be either the text of an SQL statement, in which case +the bytecode (or tables_used) for that statement is returned, or the +argument can be a parameter such as ?1 or $stmt that is later bound +to a <a href="c3ref/stmt.html">prepared statement</a> object using the +<a href="c3ref/bind_blob.html">sqlite3_bind_pointer()</a> interface. Use a pointer type of +"stmt-pointer" for the <a href="c3ref/bind_blob.html">sqlite3_bind_pointer()</a> interface. + +</p><h2 id="schema"><span>2.1. </span>Schema</h2> + +<p> +The schema of the bytecode table is: + +</p><div class="codeblock"><pre>CREATE TABLE bytecode( + addr INT, + opcode TEXT, + p1 INT, + p2 INT, + p3 INT, + p4 TEXT, + p5 INT, + comment TEXT, + subprog TEXT, + stmt HIDDEN +); +</pre></div> + +<p> +The first eight columns are the address, opcode, and operands for a +single <a href="opcode.html">bytecode</a> in the virtual machine that implements the statement. +These columns are the same columns output when using EXPLAIN. The +bytecode virtual tables shows all operations in the prepared statement, +both the main body of the prepared statement and in subprograms used +to implement triggers or foreign key actions. The "subprog" field +is NULL for the main body of the prepared statement, or is the trigger +name or the string "(FK)" for triggers and foreign key actions. + +</p><p> +The schema for the tables_used table is: + +</p><div class="codeblock"><pre>CREATE TABLE tables_used( + type TEXT, + schema TEXT, + name TEXT, + wr INT, + subprog TEXT, + stmt HIDDEN +); +</pre></div> + +<p> +The tables_used table is intended to show which btrees of the database file +are read or written by a prepared statement, both by the main statement +itself but also by related triggers and foreign key actions. The columns +are as follows: + +</p><ul> +<li><p><b>type</b> → Either "table" or "index", depending on what role +the btree is serving. + +</p></li><li><p><b>schema</b> → Which database file the btree is located in. +This will be "main" for the main database (the usual case), or "temp" for +TEMP tables and indexes, or the name assigned to <a href="lang_attach.html">attached</a> databases by +the <a href="lang_attach.html">ATTACH</a> statement. + +</p></li><li><p><b>name</b> → The name of the table or index + +</p></li><li><p><b>wr</b> → 0 if the object is read, 1 if the object is written + +</p></li><li><p><b>subprog</b> → The sub-program in which the object is +accessed. NULL means the main body of the prepared statement. Otherwise +this field is the name of a trigger or "(FK)" for a foreign key action. +</p></li></ul> +<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/bytecodevtab.in?m=fe69f4a05c">2022-01-08 05:02:57</a> UTC </small></i></p> + |