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+<title>The SQLITE_MEMSTAT Virtual Table</title>
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+<div class=fancy>
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+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>
+