Обсуждение: PostgreSQL client api
Hi,
I was testing MySQL and PgSQL performances on my home box (amd athlon
64 3000, 1gig ddr ram, sata I hdd, win xp (x86)), select and insert
times seeemed identical with innoDB.
But when i try to query both using php, there's a huge difference even
for a funny query like "select 1"
Here's the code:
<?php
$mtime = microtime(true);
$pdo = new PDO('pgsql:host=localhost;dbname=test', "testacc", "pw");
for ($i = 0; $i < 10000; $i++)
{
$result = $pdo->query("Select "+$i);
}
echo microtime(true) - $mtime;
echo "<br>";
$mtime = microtime(true);
$pdo = new PDO('mysql:host=localhost;dbname=test', "testacc", "pw");
for ($i = 0; $i < 10000; $i++)
{
$result = $pdo->query("Select "+$i);
}
echo microtime(true) - $mtime;
echo "<br>";
?>
output is:
2.7696590423584
0.89393591880798
Nearly 3 times slower even w/o any table queries. But i could not
reproduce this by writing stored procs on both which selects 0-10000 in
a loop to a variable. results were almost same.
(I tried pg_ and mysqli_ functions too, results were not too different)
Is it mysql client libraries performs better? Or postgre stored procs
are 3x faster? I cannot understand, since there is not even an io
operation or any query planning stuff, what is the cause of this?
Thanks.
On Tue, Mar 28, 2006 at 05:01:45PM -0800, Antimon wrote:
> $pdo = new PDO('pgsql:host=localhost;dbname=test', "testacc", "pw");
> for ($i = 0; $i < 10000; $i++)
> {
> $result = $pdo->query("Select "+$i);
> }
> output is:
> 2.7696590423584
Ok, so that tells me that on this plain-vanilla hardware, you can
'only' do 3600 queries per second from PHP.
Who cares?
If you're actually trying to run that kind of volume on that kind of
hardware, you need to reconsider what you're doing.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
Try factoring the connect time out of the test. My experience is the
connect is more expensive for Postgres than MySQL. With that out of the
way, I'd wager the times will be closer.
Regards,
Paul
-----Original Message-----
From: pgsql-general-owner@postgresql.org
[mailto:pgsql-general-owner@postgresql.org] On Behalf Of Antimon
Sent: Tuesday, March 28, 2006 5:02 PM
To: pgsql-general@postgresql.org
Subject: [GENERAL] PostgreSQL client api
Hi,
I was testing MySQL and PgSQL performances on my home box (amd athlon
64 3000, 1gig ddr ram, sata I hdd, win xp (x86)), select and insert
times seeemed identical with innoDB.
But when i try to query both using php, there's a huge difference even
for a funny query like "select 1"
Here's the code:
<?php
$mtime = microtime(true);
$pdo = new PDO('pgsql:host=localhost;dbname=test', "testacc", "pw");
for ($i = 0; $i < 10000; $i++)
{
$result = $pdo->query("Select "+$i);
}
echo microtime(true) - $mtime;
echo "<br>";
$mtime = microtime(true);
$pdo = new PDO('mysql:host=localhost;dbname=test', "testacc", "pw");
for ($i = 0; $i < 10000; $i++)
{
$result = $pdo->query("Select "+$i);
}
echo microtime(true) - $mtime;
echo "<br>";
?>
output is:
2.7696590423584
0.89393591880798
Nearly 3 times slower even w/o any table queries. But i could not
reproduce this by writing stored procs on both which selects 0-10000 in
a loop to a variable. results were almost same.
(I tried pg_ and mysqli_ functions too, results were not too different)
Is it mysql client libraries performs better? Or postgre stored procs
are 3x faster? I cannot understand, since there is not even an io
operation or any query planning stuff, what is the cause of this?
Thanks.
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On Tue, 2006-03-28 at 19:01, Antimon wrote:
> Hi,
> I was testing MySQL and PgSQL performances on my home box (amd athlon
> 64 3000, 1gig ddr ram, sata I hdd, win xp (x86)), select and insert
> times seeemed identical with innoDB.
>
> But when i try to query both using php, there's a huge difference even
> for a funny query like "select 1"
>
> Here's the code:
>
> <?php
> $mtime = microtime(true);
>
> $pdo = new PDO('pgsql:host=localhost;dbname=test', "testacc", "pw");
> for ($i = 0; $i < 10000; $i++)
> {
> $result = $pdo->query("Select "+$i);
> }
>
> echo microtime(true) - $mtime;
> echo "<br>";
>
> $mtime = microtime(true);
>
> $pdo = new PDO('mysql:host=localhost;dbname=test', "testacc", "pw");
> for ($i = 0; $i < 10000; $i++)
> {
> $result = $pdo->query("Select "+$i);
> }
>
> echo microtime(true) - $mtime;
> echo "<br>";
> ?>
>
> output is:
> 2.7696590423584
> 0.89393591880798
>
> Nearly 3 times slower even w/o any table queries. But i could not
> reproduce this by writing stored procs on both which selects 0-10000 in
> a loop to a variable. results were almost same.
> (I tried pg_ and mysqli_ functions too, results were not too different)
>
> Is it mysql client libraries performs better? Or postgre stored procs
> are 3x faster? I cannot understand, since there is not even an io
> operation or any query planning stuff, what is the cause of this?
MySQL's client libs, connection speed, and parser are known to be quite
fast. PostgreSQL's aren't exactly slow, but they have more to do. As
you start running actual queries, you'll see the advantage start to
disappear, and by the time you're running queries full of subselects and
unions, you'll notice the it's the tortoise and the hare all over again.
As someone else mentioned, factor out the connection time. But really,
this test is fairly bogus. Unless you're writing an app that has a lot
of "select 1" in it that is.
At least test something fairly realistic. Maybe some kind of thing like
having 10,000,000 rows, pick a number at random from 1 to 10,000,000 and
use it to select one row at a time. Better yet, make a union view with
a subselect on a function, create a functional index for the underlying
tables, and see if your outside where clause gets pushed down inside the
query by the planner.
Run updates in the background at the same time.
Pull the power plug whilst doing it, see which database comes back up.
Just benchmark what you're really gonna use the database for, cause if
you pick one or the other from this test, you might as well flip a coin.
I know this is not even a test but i thought it might be a client library issue, not server itself. Well it is not, i tried it on .net with npgsql which is a .net client library (Not using libpq). Results are same. Connect time does not have much effect by the way.
On 28 Mar 2006 17:01:45 -0800, Antimon <antimon@gmail.com> wrote: > Nearly 3 times slower even w/o any table queries. But i could not > reproduce this by writing stored procs on both which selects 0-10000 in > a loop to a variable. results were almost same. > (I tried pg_ and mysqli_ functions too, results were not too different) > > Is it mysql client libraries performs better? Or postgre stored procs > are 3x faster? I cannot understand, since there is not even an io > operation or any query planning stuff, what is the cause of this? Yes, it is the case that raw select performance for pgsql drastically improves with prepares statements as much as 2-3x. In my experience postgresql is just a bit faster with prepared statements and substantially slower without. There is a little bit of pain in setting them up properly in a pooling web environment but it is worth it if you want top performance. Does anybody know if php uses the parameterized flavors of the C API? That's another huge optimization over PQexec. I agree with Jim in that it't probably fast enough anyways. Merlin
On Wed, 2006-03-29 at 02:45, Antimon wrote: > I know this is not even a test but i thought it might be a client > library issue, not server itself. > Well it is not, i tried it on .net with npgsql which is a .net client > library (Not using libpq). Results are same. Connect time does not have > much effect by the way. Just so you understand, there was a period of time when MySQL AB put out benchmark after benchmark like this to "prove" that MySQL was faster than PostgreSQL. Of course, they never compared anything moderately complex, since they knew they'd lose. Is it a fair comparison of say, a mainframe and a workstation to compare the boot up times? Not really, unless your particular application is gonna be rebooting the mainframe a lot. It's a small, narrow channel to compare on, and most the time it doesn't mean a lot. That's all. No personal attack meant against you, sorry if it came across that way. It's just many pgsql folks still smart from that era, and it seems to come back to haunt us every so often.
Hi, I'm sorry about being understood like i was trying to compare pgsql with mysql. I was trying stuff, did this and saw that huge difference (even it is not bad alone, but comparing to mysql), and thought that might be some library issue causing slow reads from server. I don't need any rdbms to be faster on selecting a constant integer. My point was the library, not server performance.
On Wed, 2006-03-29 at 12:19, Antimon wrote: > Hi, > I'm sorry about being understood like i was trying to compare pgsql > with mysql. I was trying stuff, did this and saw that huge difference > (even it is not bad alone, but comparing to mysql), and thought that > might be some library issue causing slow reads from server. I don't > need any rdbms to be faster on selecting a constant integer. My point > was the library, not server performance. No need to apologize, honest. This discussion brings up some valid points, even if the benchmark is not necessarily a valid method for choosing the database. PostgreSQL is generally "heavier" than MySQL. A large portion of this is that PostgreSQL is generally busy making sure things are done right first, and fast second. In MySQL, it's the other way around. I wonder how your test would work if you did something a little more complex (like the pick 1 row in a million scenario) and did in parallel for say 5, 10, 20, 50 clients at a time. That would like give you some idea of how well connectivity and small sql select statements scale on each system. Generally, pgsql folks consider the single user scenario to not be that important, and ask themselves "so what happens when 50 people do this at the same time?" Again, MySQL tends to be the opposite.
Just noticed, On windows, these results are produced. But on linux, postgresql performs great. So postgre has a bad windows integration than mysql. Well since it supports win32 for a long time, it makes sense. I did some "multi client" tests and postgre could not even catch mysql so i decided to go test it on my linux box. It seems that the performance issue is about windows version.
Antimon wrote:
> Just noticed,
> On windows, these results are produced.
> But on linux, postgresql performs great. So postgre has a bad windows
> integration than mysql. Well since it supports win32 for a long time,
> it makes sense.
> I did some "multi client" tests and postgre could not even catch mysql
> so i decided to go test it on my linux box. It seems that the
> performance issue is about windows version.
Part of the problem may be the connection penalty on Windows. Since
PostgreSQL is a processed based database (mySQL is threaded I believe)
it is expensive (resource wise) to fire a bunch of connections.
You may be able to get similar performance if you were to use pconnect
or connection pooling with PHP and PostgreSQL.
Sincerely,
Joshua D. Drake
>
>
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Just tried, yes, pconnect boosts multi user performance. But causes this: http://img526.imageshack.us/img526/6302/pgsql7th.jpg :) Need to modify max persistent connection settings.
On Wed, 2006-03-29 at 15:22, Antimon wrote: > Just tried, yes, pconnect boosts multi user performance. > But causes this: > http://img526.imageshack.us/img526/6302/pgsql7th.jpg > :) > > Need to modify max persistent connection settings. I don't thin that doesn't do what you think it does. max persistent setting in php.ini sets the max number of persistent connections PER PHP / web server process. What web server is that with, btw? With a web server like lighttpd, you have a "pool" of php child processes pre-spawned and ready to go, and you limit that pool to something reasonable. With apache and other web servers, each web server child process gets its own php process hanging off of it, and if you've got, say, a default apache install, that allows up to 150 child processes. If you're using apache, you're often better off limiting the number of children to something smaller, or cranking up postgresql allowed connections to keep up. 150 is usually a bit much. 20 to 50 is normally plenty for most applications that can benefit from pconnects. But you're probably better off with something like lighttpd.
On Wed, 2006-03-29 at 15:58, Scott Marlowe wrote: > On Wed, 2006-03-29 at 15:22, Antimon wrote: > > Just tried, yes, pconnect boosts multi user performance. > > But causes this: > > http://img526.imageshack.us/img526/6302/pgsql7th.jpg > > :) > > > > Need to modify max persistent connection settings. > > I don't thin that doesn't do what you think it does. max persistent > setting in php.ini sets the max number of persistent connections PER PHP > / web server process. That should be "I don't think that does what you think it does." man, my editor is so fired...
Yes i tried and realized apache child processes.. Then i looked for another pooling solution, the project pgpool i found. No windows binaries, it might run on cygwin. After all, i think postgreSQL is not meant to run on windows production for ~2 more major releases or something. It performs great on linux thats for sure but i cannot do the platform decision everytime, so gonna stick with mySQL on windows and postgre on linux when i can.
On Wed, 2006-03-29 at 16:48, Antimon wrote: > Yes i tried and realized apache child processes.. > Then i looked for another pooling solution, the project pgpool i found. > No windows binaries, it might run on cygwin. > After all, i think postgreSQL is not meant to run on windows production > for ~2 more major releases or something. It performs great on linux > thats for sure but i cannot do the platform decision everytime, so > gonna stick with mySQL on windows and postgre on linux when i can. There's a windows version of lighttpd available. That might well do the trick. I'd still run ANY database on linux / unix before windows, just cause I don't trust windows when things go wrong to work right. But there's certainly nothing stopping you from running a linux or BSD based postgresql server behind a windows lighttpd. If the db and web server HAVE to both be on the same server, and you have to have windows, then you might want to look at firebird, which apparently has quite good windows performance, and, unlike MySQL has good SQL compliance and behaviour.