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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 14:07:11 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 14:07:11 +0000
commit63847496f14c813a5d80efd5b7de0f1294ffe1e3 (patch)
tree01c7571c7c762ceee70638549a99834fdd7c411b /www/bytecodevtab.html
parentInitial commit. (diff)
downloadsqlite3-63847496f14c813a5d80efd5b7de0f1294ffe1e3.tar.xz
sqlite3-63847496f14c813a5d80efd5b7de0f1294ffe1e3.zip
Adding upstream version 3.45.1.upstream/3.45.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<title>The Bytecode() And Tables_Used() Table-Valued Functions</title>
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+<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> &rarr; Either "table" or "index", depending on what role
+the btree is serving.
+
+</p></li><li><p><b>schema</b> &rarr; 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> &rarr; The name of the table or index
+
+</p></li><li><p><b>wr</b> &rarr; 0 if the object is read, 1 if the object is written
+
+</p></li><li><p><b>subprog</b> &rarr; 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>
+
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