Re: [rt-users] Changing database connection options?
On Mon, Dec 13, 2010 at 10:57:03AM -0500, Kevin Falcone wrote:
On Sat, Dec 11, 2010 at 11:40:17PM +0100, hubert depesz lubaczewski wrote:
Hi,
another question: is there any way to change database connections
options from config?
I.e. I want to change what's being passed as 4th argument to
DBI-connect().
You'd need to patch DBIx::SearchBuilder to provide an option for RT to
use and then patch RT to use that option.
Hmm. This looks like a very complicated task. Wouldn't it be possible,
to just call:
$dbh-{'pg_server_prepare'} = 0;
from rt?
Reason - server side prepared statements are rarely useful, usually they
do not speed things up, and they break some setups.
Of course I can modify my own copy of rt, but patching it again and
again after every upgrade seems to be suboptimal.
Best regards,
depesz
--
Linkedin: http://www.linkedin.com/in/depesz / blog: http://www.depesz.com/
jid/gtalk: dep...@depesz.com / aim:depeszhdl / skype:depesz_hdl / gg:6749007
Re: [rt-users] Changing database connection options?
On Tue, Dec 14, 2010 at 02:18:13PM +0100, hubert depesz lubaczewski wrote:
On Mon, Dec 13, 2010 at 10:57:03AM -0500, Kevin Falcone wrote:
On Sat, Dec 11, 2010 at 11:40:17PM +0100, hubert depesz lubaczewski wrote:
Hi,
another question: is there any way to change database connections
options from config?
I.e. I want to change what's being passed as 4th argument to
DBI-connect().
You'd need to patch DBIx::SearchBuilder to provide an option for RT to
use and then patch RT to use that option.
Hmm. This looks like a very complicated task. Wouldn't it be possible,
to just call:
I'm delineating the right way to do it.
$dbh-{'pg_server_prepare'} = 0;
from rt?
Reason - server side prepared statements are rarely useful, usually they
do not speed things up, and they break some setups.
Of course I can modify my own copy of rt, but patching it again and
again after every upgrade seems to be suboptimal.
I'm leery to make a change like that for RT without knowing much more
about why I should be making it.
-kevin
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Re: [rt-users] Changing database connection options?
On Tue, Dec 14, 2010 at 10:43:18AM -0500, Kevin Falcone wrote:
I'm delineating the right way to do it.
$dbh-{'pg_server_prepare'} = 0;
from rt?
Reason - server side prepared statements are rarely useful, usually they
do not speed things up, and they break some setups.
Of course I can modify my own copy of rt, but patching it again and
again after every upgrade seems to be suboptimal.
I'm leery to make a change like that for RT without knowing much more
about why I should be making it.
I am willing to provide all kind of information if you'd need.
the biggest problem with server side prepared statements is described
with examples in here:
http://www.depesz.com/index.php/2008/05/10/prepared-statements-gotcha/
they (server side prepared statements) make sense if you:
1. use complicated queries with many joins
2. in the time of single db connection you run given query many times
3. if you change parameters to the query - you don't change the ones
that can influence execution plan.
all in all - (in my opinion) chances of this are very slim, and in rt -
i haven't seen anything even resembling such queries.
on the other hand - there is program called pgbouncer. which is
connection pooler with great ability to reuse connection as soon as it
finishes transaction.
this is great from performance and resources-consumption standpoint, but
breaks if you use server side prepared statements - because they are
being used across many transactions.
finally - when using short, simple queries - prepared statements can
actually work worse than normal queries, because they need more
roundtrips client-server to do the same task.
Best regards,
depesz
--
Linkedin: http://www.linkedin.com/in/depesz / blog: http://www.depesz.com/
jid/gtalk: dep...@depesz.com / aim:depeszhdl / skype:depesz_hdl / gg:6749007
Re: [rt-users] Changing database connection options?
finally - when using short, simple queries - prepared statements can actually work worse than normal queries, because they need more roundtrips client-server to do the same task. I suspect we'd need to see benchmarks of RT on versions of postgres from 8.1 - 9 to be able to really evaluate that. I'd hate to make someone else's performance worse. Adding a way for you to frob it to RT from the Connect code might be possible, but it'd need to be a config option. -kevin pgpk9BvA3nMA7.pgp Description: PGP signature
Re: [rt-users] Changing database connection options?
On Sat, Dec 11, 2010 at 11:40:17PM +0100, hubert depesz lubaczewski wrote:
Hi,
another question: is there any way to change database connections
options from config?
I.e. I want to change what's being passed as 4th argument to
DBI-connect().
You'd need to patch DBIx::SearchBuilder to provide an option for RT to
use and then patch RT to use that option.
-kevin
Reason for this is pretty simple: I'm using PostgreSQL, and DBD::Pg is
choosing by default to use server side prepared statements. I don't like
them, and would like to disable them, but I'd prefer not to modify RT
source itself, so I was hoping for some way to make it happen from
config.
To show some example.
When $dbh is created like this;
$dbh = DBI-connect( 'dbi:Pg:dbname=xxx', 'yy', 'zz' );
DBD::Pg will use server side prepared statements.
To disable this feature, one have to either:
$dbh-{pg_server_prepare} = 0;
or:
$dbh = DBI-connect( 'dbi:Pg:dbname=xxx', 'yy', 'zz', { pg_server_prepare =
0 } );
In case you need to know why i want to disable server side prepared
statements:
1. http://www.depesz.com/index.php/2008/05/10/prepared-statements-gotcha/
2. it breaks connection pooling with pgbouncer (and I know I can use
different pooling mode, but session pooling is pretty much useless)
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