speed.tcl

sqlite嵌入式数据库源码

#
# Run this Tcl script to generate the speed.html file.
#
set rcsid {$Id: speed.tcl,v 1.17 2005/03/12 15:55:11 drh Exp $ }
source common.tcl
header {SQLite Database Speed Comparison}

puts {
<h2>Database Speed Comparison</h2>

<font color="red"><b>
Note:  This document is old.  It describes a speed comparison between
an older version of SQLite against archaic versions of MySQL and PostgreSQL.
Readers are invited to contribute more up-to-date speed comparisons
on the <a href="http://www.sqlite.org/cvstrac/wiki">SQLite Wiki</a>.
<p>
The numbers here are old enough to be nearly meaningless.  Until it is
updated, use this document only as proof that SQLite is not a
sluggard.
</b></font>

<h3>Executive Summary</h3>

<p>A series of tests were run to measure the relative performance of
SQLite 2.7.6, PostgreSQL 7.1.3, and MySQL 3.23.41.
The following are general
conclusions drawn from these experiments:
</p>

<ul>
<li><p>
  SQLite 2.7.6 is significantly faster (sometimes as much as 10 or
  20 times faster) than the default PostgreSQL 7.1.3 installation
  on RedHat 7.2 for most common operations.  
</p></li>
<li><p>
  SQLite 2.7.6 is often faster (sometimes
  more than twice as fast) than MySQL 3.23.41
  for most common operations.
</p></li>
<li><p>
  SQLite does not execute CREATE INDEX or DROP TABLE as fast as
  the other databases.  But this is not seen as a problem because
  those are infrequent operations.
</p></li>
<li><p>
  SQLite works best if you group multiple operations together into
  a single transaction.
</p></li>
</ul>

<p>
The results presented here come with the following caveats:
</p>

<ul>
<li><p>
  These tests did not attempt to measure multi-user performance or
  optimization of complex queries involving multiple joins and subqueries.
</p></li>
<li><p>
  These tests are on a relatively small (approximately 14 megabyte) database.
  They do not measure how well the database engines scale to larger problems.
</p></li>
</ul>

<h3>Test Environment</h3>

<p>
The platform used for these tests is a 1.6GHz Athlon with 1GB or memory
and an IDE disk drive.  The operating system is RedHat Linux 7.2 with
a stock kernel.
</p>

<p>
The PostgreSQL and MySQL servers used were as delivered by default on
RedHat 7.2.  (PostgreSQL version 7.1.3 and MySQL version 3.23.41.)
No effort was made to tune these engines.  Note in particular
the the default MySQL configuration on RedHat 7.2 does not support
transactions.  Not having to support transactions gives MySQL a
big speed advantage, but SQLite is still able to hold its own on most
tests.
</p>

<p>
I am told that the default PostgreSQL configuration in RedHat 7.3
is unnecessarily conservative (it is designed to
work on a machine with 8MB of RAM) and that PostgreSQL could
be made to run a lot faster with some knowledgeable configuration
tuning.
Matt Sergeant reports that he has tuned his PostgreSQL installation
and rerun the tests shown below.  His results show that
PostgreSQL and MySQL run at about the same speed.  For Matt's
results, visit
</p>

<blockquote>
<a href="http://www.sergeant.org/sqlite_vs_pgsync.html">
http://www.sergeant.org/sqlite_vs_pgsync.html</a>
</blockquote>

<p>
SQLite was tested in the same configuration that it appears
on the website.  It was compiled with -O6 optimization and with
the -DNDEBUG=1 switch which disables the many "assert()" statements
in the SQLite code.  The -DNDEBUG=1 compiler option roughly doubles
the speed of SQLite.
</p>

<p>
All tests are conducted on an otherwise quiescent machine.
A simple Tcl script was used to generate and run all the tests.
A copy of this Tcl script can be found in the SQLite source tree
in the file <b>tools/speedtest.tcl</b>.
</p>

<p>
The times reported on all tests represent wall-clock time 
in seconds.  Two separate time values are reported for SQLite.
The first value is for SQLite in its default configuration with
full disk synchronization turned on.  With synchronization turned
on, SQLite executes
an <b>fsync()</b> system call (or the equivalent) at key points
to make certain that critical data has 
actually been written to the disk drive surface.  Synchronization
is necessary to guarantee the integrity of the database if the
operating system crashes or the computer powers down unexpectedly
in the middle of a database update.  The second time reported for SQLite is
when synchronization is turned off.  With synchronization off,
SQLite is sometimes much faster, but there is a risk that an
operating system crash or an unexpected power failure could
damage the database.  Generally speaking, the synchronous SQLite
times are for comparison against PostgreSQL (which is also
synchronous) and the asynchronous SQLite times are for 
comparison against the asynchronous MySQL engine.
</p>

<h3>Test 1: 1000 INSERTs</h3>
<blockquote>
CREATE TABLE t1(a INTEGER, b INTEGER, c VARCHAR(100));<br>
INSERT INTO t1 VALUES(1,13153,'thirteen thousand one hundred fifty three');<br>
INSERT INTO t1 VALUES(2,75560,'seventy five thousand five hundred sixty');<br>
<i>... 995 lines omitted</i><br>
INSERT INTO t1 VALUES(998,66289,'sixty six thousand two hundred eighty nine');<br>
INSERT INTO t1 VALUES(999,24322,'twenty four thousand three hundred twenty two');<br>
INSERT INTO t1 VALUES(1000,94142,'ninety four thousand one hundred forty two');<br>

</blockquote><table border=0 cellpadding=0 cellspacing=0>
<tr><td>PostgreSQL:</td><td align="right">&nbsp;&nbsp;&nbsp;4.373</td></tr>
<tr><td>MySQL:</td><td align="right">&nbsp;&nbsp;&nbsp;0.114</td></tr>
<tr><td>SQLite 2.7.6:</td><td align="right">&nbsp;&nbsp;&nbsp;13.061</td></tr>
<tr><td>SQLite 2.7.6 (nosync):</td><td align="right">&nbsp;&nbsp;&nbsp;0.223</td></tr>
</table>

<p>
Because it does not have a central server to coordinate access,
SQLite must close and reopen the database file, and thus invalidate
its cache, for each transaction.  In this test, each SQL statement
is a separate transaction so the database file must be opened and closed
and the cache must be flushed 1000 times.  In spite of this, the asynchronous
version of SQLite is still nearly as fast as MySQL.  Notice how much slower
the synchronous version is, however.  SQLite calls <b>fsync()</b> after 
each synchronous transaction to make sure that all data is safely on
the disk surface before continuing.  For most of the 13 seconds in the
synchronous test, SQLite was sitting idle waiting on disk I/O to complete.</p>


<h3>Test 2: 25000 INSERTs in a transaction</h3>
<blockquote>
BEGIN;<br>
CREATE TABLE t2(a INTEGER, b INTEGER, c VARCHAR(100));<br>
INSERT INTO t2 VALUES(1,59672,'fifty nine thousand six hundred seventy two');<br>
<i>... 24997 lines omitted</i><br>
INSERT INTO t2 VALUES(24999,89569,'eighty nine thousand five hundred sixty nine');<br>
INSERT INTO t2 VALUES(25000,94666,'ninety four thousand six hundred sixty six');<br>
COMMIT;<br>

</blockquote><table border=0 cellpadding=0 cellspacing=0>
<tr><td>PostgreSQL:</td><td align="right">&nbsp;&nbsp;&nbsp;4.900</td></tr>
<tr><td>MySQL:</td><td align="right">&nbsp;&nbsp;&nbsp;2.184</td></tr>
<tr><td>SQLite 2.7.6:</td><td align="right">&nbsp;&nbsp;&nbsp;0.914</td></tr>
<tr><td>SQLite 2.7.6 (nosync):</td><td align="right">&nbsp;&nbsp;&nbsp;0.757</td></tr>
</table>

<p>
When all the INSERTs are put in a transaction, SQLite no longer has to
close and reopen the database or invalidate its cache between each statement.
It also does not
have to do any fsync()s until the very end.  When unshackled in
this way, SQLite is much faster than either PostgreSQL and MySQL.
</p>

<h3>Test 3: 25000 INSERTs into an indexed table</h3>
<blockquote>
BEGIN;<br>
CREATE TABLE t3(a INTEGER, b INTEGER, c VARCHAR(100));<br>
CREATE INDEX i3 ON t3(c);<br>
<i>... 24998 lines omitted</i><br>
INSERT INTO t3 VALUES(24999,88509,'eighty eight thousand five hundred nine');<br>
INSERT INTO t3 VALUES(25000,84791,'eighty four thousand seven hundred ninety one');<br>
COMMIT;<br>

</blockquote><table border=0 cellpadding=0 cellspacing=0>
<tr><td>PostgreSQL:</td><td align="right">&nbsp;&nbsp;&nbsp;8.175</td></tr>
<tr><td>MySQL:</td><td align="right">&nbsp;&nbsp;&nbsp;3.197</td></tr>
<tr><td>SQLite 2.7.6:</td><td align="right">&nbsp;&nbsp;&nbsp;1.555</td></tr>
<tr><td>SQLite 2.7.6 (nosync):</td><td align="right">&nbsp;&nbsp;&nbsp;1.402</td></tr>
</table>

<p>
There were reports that SQLite did not perform as well on an indexed table.
This test was recently added to disprove those rumors.  It is true that
SQLite is not as fast at creating new index entries as the other engines
(see Test 6 below) but its overall speed is still better.
</p>

<h3>Test 4: 100 SELECTs without an index</h3>
<blockquote>
BEGIN;<br>
SELECT count(*), avg(b) FROM t2 WHERE b>=0 AND b<1000;<br>
SELECT count(*), avg(b) FROM t2 WHERE b>=100 AND b<1100;<br>
<i>... 96 lines omitted</i><br>
SELECT count(*), avg(b) FROM t2 WHERE b>=9800 AND b<10800;<br>
SELECT count(*), avg(b) FROM t2 WHERE b>=9900 AND b<10900;<br>
COMMIT;<br>

</blockquote><table border=0 cellpadding=0 cellspacing=0>
<tr><td>PostgreSQL:</td><td align="right">&nbsp;&nbsp;&nbsp;3.629</td></tr>
<tr><td>MySQL:</td><td align="right">&nbsp;&nbsp;&nbsp;2.760</td></tr>
<tr><td>SQLite 2.7.6:</td><td align="right">&nbsp;&nbsp;&nbsp;2.494</td></tr>
<tr><td>SQLite 2.7.6 (nosync):</td><td align="right">&nbsp;&nbsp;&nbsp;2.526</td></tr>
</table>


<p>
This test does 100 queries on a 25000 entry table without an index,
thus requiring a full table scan.   Prior versions of SQLite used to
be slower than PostgreSQL and MySQL on this test, but recent performance
enhancements have increased its speed so that it is now the fastest
of the group.
</p>

<h3>Test 5: 100 SELECTs on a string comparison</h3>
<blockquote>
BEGIN;<br>
SELECT count(*), avg(b) FROM t2 WHERE c LIKE '%one%';<br>
SELECT count(*), avg(b) FROM t2 WHERE c LIKE '%two%';<br>
<i>... 96 lines omitted</i><br>