pragma.html

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    </p>
    <p>In SQLite version 2, the default value is NORMAL. For version 3, the
    default was changed to FULL.
    </p>
</li>



<a name="pragma_temp_store"></a>

<li><p><b>PRAGMA temp_store;
       <br>PRAGMA temp_store = DEFAULT;</b> (0)<b>
       <br>PRAGMA temp_store = FILE;</b> (1)<b>
       <br>PRAGMA temp_store = MEMORY;</b> (2)</p>
    <p>Query or change the setting of the "<b>temp_store</b>" parameter.
    When temp_store is DEFAULT (0), the compile-time C preprocessor macro
    TEMP_STORE is used to determine where temporary tables and indices
    are stored.  When
    temp_store is MEMORY (2) temporary tables and indices are kept in memory.
    When temp_store is FILE (1) temporary tables and indices are stored
    in a file.  The <a href="#pragma_temp_store_directory">
    temp_store_directory</a> pragma can be used to specify the directory
    containing this file.
    <b>FILE</b> is specified. When the temp_store setting is changed,
    all existing temporary tables, indices, triggers, and views are
    immediately deleted.</p>

    <p>It is possible for the library compile-time C preprocessor symbol
    TEMP_STORE to override this pragma setting.  The following table summarizes
    the interaction of the TEMP_STORE preprocessor macro and the
    temp_store pragma:</p>

    <blockquote>
    <table cellpadding="2" border="1">
    <tr><th valign="bottom">TEMP_STORE</th>
        <th valign="bottom">PRAGMA<br>temp_store</th>
        <th>Storage used for<br>TEMP tables and indices</th></tr>
    <tr><td align="center">0</td>
        <td align="center"><em>any</em></td>
        <td align="center">file</td></tr>
    <tr><td align="center">1</td>
        <td align="center">0</td>
        <td align="center">file</td></tr>
    <tr><td align="center">1</td>
        <td align="center">1</td>
        <td align="center">file</td></tr>
    <tr><td align="center">1</td>
        <td align="center">2</td>
        <td align="center">memory</td></tr>
    <tr><td align="center">2</td>
        <td align="center">0</td>
        <td align="center">memory</td></tr>
    <tr><td align="center">2</td>
        <td align="center">1</td>
        <td align="center">file</td></tr>
    <tr><td align="center">2</td>
        <td align="center">2</td>
        <td align="center">memory</td></tr>
    <tr><td align="center">3</td>
        <td align="center"><em>any</em></td>
        <td align="center">memory</td></tr>
    </table>
    </blockquote>
    </li>
    <br>


<a name="pragma_temp_store_directory"></a>

<li><p><b>PRAGMA temp_store_directory;
       <br>PRAGMA temp_store_directory = 'directory-name';</b></p>
    <p>Query or change the setting of the "temp_store_directory" - the
    directory where files used for storing temporary tables and indices
    are kept.  This setting lasts for the duration of the current connection
    only and resets to its default value for each new connection opened.

    <p>When the temp_store_directory setting is changed, all existing temporary
    tables, indices, triggers, and viewers are immediately deleted.  In
    practice, temp_store_directory should be set immediately after the 
    database is opened.  </p>

    <p>The value <i>directory-name</i> should be enclosed in single quotes.
    To revert the directory to the default, set the <i>directory-name</i> to
    an empty string, e.g., <i>PRAGMA temp_store_directory = ''</i>.  An
    error is raised if <i>directory-name</i> is not found or is not
    writable. </p>

    <p>The default directory for temporary files depends on the OS.  For
    Unix/Linux/OSX, the default is the is the first writable directory found
    in the list of: <b>/var/tmp, /usr/tmp, /tmp,</b> and <b>
    <i>current-directory</i></b>.  For Windows NT, the default 
    directory is determined by Windows, generally
    <b>C:\Documents and Settings\<i>user-name</i>\Local Settings\Temp\</b>. 
    Temporary files created by SQLite are unlinked immediately after
    opening, so that the operating system can automatically delete the
    files when the SQLite process exits.  Thus, temporary files are not
    normally visible through <i>ls</i> or <i>dir</i> commands.</p>
 
    </li>
</ul>



<hr />
<a name="schema"></a>
<h1>Pragmas to query the database schema</h1>



<ul>

<a name="pragma_database_list"></a>

<li><p><b>PRAGMA database_list;</b></p>
    <p>For each open database, invoke the callback function once with
    information about that database.  Arguments include the index and 
    the name the database was attached with.  The first row will be for 
    the main database.  The second row will be for the database used to 
    store temporary tables.</p></li>


<a name="pragma_foreign_key_list"></a>

<li><p><b>PRAGMA foreign_key_list(</b><i>table-name</i><b>);</b></p>
    <p>For each foreign key that references a column in the argument
    table, invoke the callback function with information about that
    foreign key. The callback function will be invoked once for each
    column in each foreign key.</p></li>


<a name="pragma_freelist_count"></a>

<li><p><b>PRAGMA &#91;database&#93;.freelist_count;</b></p>
    <p>Return the number of unused pages in the database file. Running
    a <a href="#pragma_incremental_vacuum">"PRAGMA incremental_vaccum(N);"</a> 
    command with a large value of N will shrink the database file by this
    number of pages. </p></li>


<a name="pragma_index_info"></a>

<li><p><b>PRAGMA index_info(</b><i>index-name</i><b>);</b></p>
    <p>For each column that the named index references, invoke the 
    callback function
    once with information about that column, including the column name,
    and the column number.</p></li>


<a name="pragma_index_list"></a>

<li><p><b>PRAGMA index_list(</b><i>table-name</i><b>);</b></p>
    <p>For each index on the named table, invoke the callback function
    once with information about that index.  Arguments include the
    index name and a flag to indicate whether or not the index must be
    unique.</p></li>


<a name="pragma_table_info"></a>

<li><p><b>PRAGMA table_info(</b><i>table-name</i><b>);</b></p>
    <p>For each column in the named table, invoke the callback function
    once with information about that column, including the column name,
    data type, whether or not the column can be NULL, and the default
    value for the column.</p></li>
</ul>



<hr />
<a name="version"></a>
<h1>Pragmas to query/modify version values</h1>



<ul>

<a name="pragma_schema_version"></a>
<a name="pragma_user_version"></a>

<li><p><b>PRAGMA &#91;database.&#93;schema_version; 
       <br>PRAGMA &#91;database.&#93;schema_version = </b><i>integer </i><b>;
       <br>PRAGMA &#91;database.&#93;user_version;
       <br>PRAGMA &#91;database.&#93;user_version = </b><i>integer </i><b>;</b>

  
<p>    The pragmas schema_version and user_version are used to set or get
       the value of the schema-version and user-version, respectively. Both
       the schema-version and the user-version are 32-bit signed integers
       stored in the database header.</p>
  
<p>    The schema-version is usually only manipulated internally by SQLite.  
       It is incremented by SQLite whenever the database schema is modified 
       (by creating or dropping a table or index). The schema version is 
       used by SQLite each time a query is executed to ensure that the 
       internal cache of the schema used when compiling the SQL query matches 
       the schema of the database against which the compiled query is actually 
       executed.  Subverting this mechanism by using "PRAGMA schema_version" 
       to modify the schema-version is potentially dangerous and may lead 
       to program crashes or database corruption. Use with caution!</p>
  
<p>    The user-version is not used internally by SQLite. It may be used by
       applications for any purpose.</p>
</li>
</ul>



<hr />
<a name="debug"></a>
<h1>Pragmas to debug the library</h1>



<ul>

<a name="pragma_integrity_check"></a>

<li><p><b>PRAGMA integrity_check;
    <br>PRAGMA integrity_check(</b><i>integer</i><b>)</b></p>
    <p>The command does an integrity check of the entire database.  It
    looks for out-of-order records, missing pages, malformed records, and
    corrupt indices.
    If any problems are found, then strings are returned (as multiple
    rows with a single column per row) which describe
    the problems.  At most <i>integer</i> errors will be reported
    before the analysis quits.  The default value for <i>integer</i>
    is 100.  If no errors are found, a single row with the value "ok" is
    returned.</p></li>


<a name="pragma_parser_trace"></a>

<li><p><b>PRAGMA parser_trace = ON; </b>(1)<b>
    <br>PRAGMA parser_trace = OFF;</b> (0)</p>
    <p>Turn tracing of the SQL parser inside of the
    SQLite library on and off.  This is used for debugging.
    This only works if the library is compiled without the NDEBUG macro.
    </p></li>


<a name="pragma_vdbe_trace"></a>

<li><p><b>PRAGMA vdbe_trace = ON; </b>(1)<b>
    <br>PRAGMA vdbe_trace = OFF;</b> (0)</p>
    <p>Turn tracing of the virtual database engine inside of the
    SQLite library on and off.  This is used for debugging.  See the 
    <a href="vdbe.html#trace">VDBE documentation</a> for more 
    information.</p></li>


<a name="pragma_vdbe_listing"></a>

<li><p><b>PRAGMA vdbe_listing = ON; </b>(1)<b>
    <br>PRAGMA vdbe_listing = OFF;</b> (0)</p>
    <p>Turn listings of virtual machine programs on and off.
    With listing is on, the entire content of a program is printed
    just prior to beginning execution.  This is like automatically
    executing an 
<a href="lang_explain.html">EXPLAIN</a> prior to each statement.  The statement
    executes normally after the listing is printed.
    This is used for debugging.  See the 
    <a href="vdbe.html#trace">VDBE documentation</a> for more 
    information.</p></li>
</ul>

<hr><small<i>
This page last modified 2007/12/20 20:49:53 UTC
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