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Overview
| Comment: | - Added entries for PRAGMAs database_list, temp_store and default_temp_store. - Fixed missing end tags. (CVS 960) |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
55ae7b35ee2dcebc99256d4b1e22a87e |
| User & Date: | jplyon 2003-05-07 04:04:17.000 |
Context
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2003-05-07
| ||
| 13:37 | Format keyword lists in lang.html using a TCL proc. (CVS 961) (check-in: ca75f1ca12 user: drh tags: trunk) | |
| 04:04 | - Added entries for PRAGMAs database_list, temp_store and default_temp_store. - Fixed missing end tags. (CVS 960) (check-in: 55ae7b35ee user: jplyon tags: trunk) | |
| 03:59 | Cleaned up keywords section. (CVS 959) (check-in: bb609f96e0 user: jplyon tags: trunk) | |
Changes
Changes to www/lang.tcl.
1 2 3 | # # Run this Tcl script to generate the sqlite.html file. # | | | 1 2 3 4 5 6 7 8 9 10 11 |
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: lang.tcl,v 1.55 2003/05/07 04:04:17 jplyon Exp $}
puts {<html>
<head>
<title>Query Language Understood By SQLite</title>
</head>
<body bgcolor=white>
<h1 align=center>
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The pragma command is experimental and specific pragma statements may be
removed or added in future releases of SQLite. Use this command
with caution.</p>
<p>The current implementation supports the following pragmas:</p>
<ul>
<li><p><b>PRAGMA cache_size;
<br>PRAGMA cache_size = </b><i>Number-of-pages</i><b>;</b></p>
<p>Query or change the maximum number of database disk pages that SQLite
will hold in memory at once. Each page uses about 1.5K of memory.
The default cache size is 2000. If you are doing UPDATEs or DELETEs
that change many rows of a database and you do not mind if SQLite
uses more memory, you can increase the cache size for a possible speed
improvement.</p>
<p>When you change the cache size using the cache_size pragma, the
change only endures for the current session. The cache size reverts
to the default value when the database is closed and reopened. Use
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The pragma command is experimental and specific pragma statements may be
removed or added in future releases of SQLite. Use this command
with caution.</p>
<p>The current implementation supports the following pragmas:</p>
<ul>
<a name="pragma_cache_size"></a>
<li><p><b>PRAGMA cache_size;
<br>PRAGMA cache_size = </b><i>Number-of-pages</i><b>;</b></p>
<p>Query or change the maximum number of database disk pages that SQLite
will hold in memory at once. Each page uses about 1.5K of memory.
The default cache size is 2000. If you are doing UPDATEs or DELETEs
that change many rows of a database and you do not mind if SQLite
uses more memory, you can increase the cache size for a possible speed
improvement.</p>
<p>When you change the cache size using the cache_size pragma, the
change only endures for the current session. The cache size reverts
to the default value when the database is closed and reopened. Use
the <a href="#pragma_default_cache_size"><b>default_cache_size</b></a>
pragma to check the cache size permanently.</p></li>
<li><p><b>PRAGMA count_changes = ON;
<br>PRAGMA count_changes = OFF;</b></p>
<p>When on, the COUNT_CHANGES pragma causes the callback function to
be invoked once for each DELETE, INSERT, or UPDATE operation. The
argument is the number of rows that were changed.</p>
<p>This pragma may be removed from future versions of SQLite.
Consider using the <b>sqlite_changes()</b> API function instead.</p></li>
<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 datbase 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_default_cache_size"></a>
<li><p><b>PRAGMA default_cache_size;
<br>PRAGMA default_cache_size = </b><i>Number-of-pages</i><b>;</b></p>
<p>Query or change the maximum number of database disk pages that SQLite
will hold in memory at once. Each page uses about 1.5K of memory.
This pragma works like the <a href="#pragma_cache_size"><b>cache_size</b></a>
pragma with the additional
feature that it changes the cache size persistently. With this pragma,
you can set the cache size once and that setting is retained and reused
everytime you reopen the database.</p></li>
<a name="pragma_default_synchronous"></a>
<li><p><b>PRAGMA default_synchronous;
<br>PRAGMA default_synchronous = FULL;
<br>PRAGMA default_synchronous = NORMAL;
<br>PRAGMA default_synchronous = OFF;</b></p>
<p>Query or change the setting of the "synchronous" flag in
the database. When synchronous is FULL, the SQLite database engine will
pause at critical moments to make sure that data has actually been
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the database might become corrupted if the operating system
crashes or the computer loses power before that data has been written
to the disk surface. On the other hand, some
operations are as much as 50 or more times faster with synchronous OFF.
</p>
<p>This pragma changes the synchronous mode persistently. Once changed,
the mode stays as set even if the database is closed and reopened. The
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the database might become corrupted if the operating system
crashes or the computer loses power before that data has been written
to the disk surface. On the other hand, some
operations are as much as 50 or more times faster with synchronous OFF.
</p>
<p>This pragma changes the synchronous mode persistently. Once changed,
the mode stays as set even if the database is closed and reopened. The
<a href="#pragma_synchronous"><b>synchronous</b></a> pragma does the same
thing but only applies the setting to the current session.</p></li>
<a name="pragma_default_temp_store"></a>
<li><p><b>PRAGMA default_temp_store;
<br>PRAGMA default_temp_store = DEFAULT;
<br>PRAGMA default_temp_store = MEMORY;
<br>PRAGMA default_temp_store = FILE;</b></p>
<p>Query or change the setting of the "temp_store" flag stored in
the database. When temp_store is DEFAULT, the compile-time default
is used for the temporary database. When temp_store is MEMORY, an
in-memory database is used. When temp_store is FILE, a temporary
database file on disk will be used. Note that it is possible for
the library compile-time options to override this setting. Once
the temporary database is in use, its location cannot be changed.</p>
<p>This pragma changes the temp_store mode persistently. Once changed,
the mode stays as set even if the database is closed and reopened. The
<a href="#pragma_temp_store"><b>temp_store</b></a> pragma does the same
thing but only applies the setting to the current session.</p></li>
<a name="pragma_empty_result_callbacks"></a>
<li><p><b>PRAGMA empty_result_callbacks = ON;
<br>PRAGMA empty_result_callbacks = OFF;</b></p>
<p>When on, the EMPTY_RESULT_CALLBACKS pragma causes the callback
function to be invoked once for each query that has an empty result
set. The third "<b>argv</b>" parameter to the callback is set to NULL
because there is no data to report. But the second "<b>argc</b>" and
fourth "<b>columnNames</b>" parameters are valid and can be used to
determine the number and names of the columns that would have been in
the result set had the set not been empty.</p></li>
<li><p><b>PRAGMA full_column_names = ON;
<br>PRAGMA full_column_names = OFF;</b></p>
<p>The column names reported in an SQLite callback are normally just
the name of the column itself, except for joins when "TABLE.COLUMN"
is used. But when full_column_names is turned on, column names are
always reported as "TABLE.COLUMN" even for simple queries.</p></li>
<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>
<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>
<li><p><b>PRAGMA integrity_check;</b></p>
<p>The command does an integrity check of the entire database. It
looks for out-of-order records, missing pages, and malformed records.
If any problems are found, then a single string is returned which is
a description of all problems. If everything is in order, "ok" is
returned.</p></li>
<li><p><b>PRAGMA parser_trace = ON;<br>PRAGMA parser_trace = OFF;</b></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_show_datatypes"></a>
<li><p><b>PRAGMA show_datatypes = ON;<br>PRAGMA show_datatypes = OFF;</b></p>
<p>When turned on, the SHOW_DATATYPES pragma causes extra entries containing
the names of <a href="datatypes.html">datatypes</a> of columns to be
appended to the 4th ("columnNames") argument to <b>sqlite_exec()</b>
callbacks. When
turned off, the 4th argument to callbacks contains only the column names.
The datatype for table columns is taken from the CREATE TABLE statement
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azCol[2] = "empty";<br>
azCol[3] = "TEXT";<br>
azCol[4] = "NUMERIC";<br>
azCol[5] = "TEXT";<br>
azCol[6] = 0;
</td></table></blockquote></li>
<li><p><b>PRAGMA synchronous;
<br>PRAGMA synchronous = FULL;
<br>PRAGMA synchronous = NORMAL;
<br>PRAGMA synchronous = OFF;</b></p>
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azCol[2] = "empty";<br>
azCol[3] = "TEXT";<br>
azCol[4] = "NUMERIC";<br>
azCol[5] = "TEXT";<br>
azCol[6] = 0;
</td></table></blockquote></li>
<a name="pragma_synchronous"></a>
<li><p><b>PRAGMA synchronous;
<br>PRAGMA synchronous = FULL;
<br>PRAGMA synchronous = NORMAL;
<br>PRAGMA synchronous = OFF;</b></p>
<p>Query or change the setting of the "synchronous" flag affecting
the database for the duration of the current database connection.
The synchronous flag reverts to its default value when the database
is closed and reopened. For additional information on the synchronous
flag, see the description of the <a href="#pragma_default_synchronous">
<b>default_synchronous</b></a> pragma.</p>
</li>
<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>
<a name="pragma_temp_store"></a>
<li><p><b>PRAGMA temp_store;
<br>PRAGMA temp_store = default;
<br>PRAGMA temp_store = memory;
<br>PRAGMA temp_store = file;</b></p>
<p>Query or change the setting of the "temp_store" flag affecting
the database for the duration of the current database connection.
The temp_store flag reverts to its default value when the database
is closed and reopened. For additional information on the temp_store
flag, see the description of the <a href="#pragma_default_temp_store">
<b>default_temp_store</b></a> pragma. Note that it is possible for
the library compile-time options to override this setting. </p>
</li>
<li><p><b>PRAGMA vdbe_trace = ON;<br>PRAGMA vdbe_trace = OFF;</b></p>
<p>Turn tracing of the virtual database engine inside of the
SQLite library on and off. This is used for debugging.</p></li>
</ul>
<p>No error message is generated if an unknown pragma is issued.
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