On Mar 19, 2010, at 12:59 PM, Matt Newell wrote:
On Friday 19 March 2010 12:06:12 Scott Frankel wrote:
Hi all,
Would anyone have any suggestions for improving QSqlDatabase PSQL
connection performance?
The Qt docs refer to PSQL connection options and demonstrate the
"requiressl=1" example. Are there other options that can be set?
(eg: the docs' PostgreSQL "options" bullet point) Google searches
are coming up short.
I note that my local postgresql.conf file has a "work_mem" statement.
(Usage: work_mem = 1MB) That could be germane, but including the
term in my setConnectOptions() method (as part of a semi-colon
separated list) yields PSQL errors.
I've optimized my working code further. Running from a local data
set, launch times are down to 4 seconds. Running from an identical
data set hosted remotely, my application launches in 40+ seconds!
Thanks in advance!
Scott
I always disable prepared connection inside the qsqlpsql driver,
just add a
return false; line after the PreparedQueries case statement in the
hasFeatures function(that's all from memory, names may be off).
This will
only help if you are using QSqlQuery.prepare, which i use for the api
convenience, not because i actually want prepared queries. This
will reduce
the roundtrip count and could make a difference if roundtrip time is
an
issue.
I use prepared statements sparingly and only for inserts back to the db.
On the server you should enable logging of queries that take over a
certain
amount of time. This will help you narrow down places where you
need indexes
or better designed queries.
Good idea.
Also it's possible to use multiple connection each from it's own
thread. I
haven't done this in pyqt alone, but have done this quite a lot in c+
+/qt
apps.
My initial forays into multithreading yielded warnings about pixmaps
when I attempted to thread form construction as a whole. I'll look
into threading just the data load portions.
Other than that just reducing the total number of queries, which can
be done
by more intelligent/complex queries, or by stored procedures.
Yes. Most of my recent effort has been replacing queries with data
model operations.
The qsqlpsql driver is a fairly thin wrapper around psql so I don't
really
think there is a lot of performance gains to be had by changing any
settings.
Thanks for the info!
Matt
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