Yes,
I have vacuumed it and also rebuild the indexes to no avail. :-(
I am not a PostgreSQL expert (and not even an expert DBA in general),
so it is very possible that I am doing something very wrong.
This is both a good news (the application should be fine, and I don't
need to tune it much further) and bad news (I need to learn how to
tune a PostgreSQL db, or find someone that could help).
Best regards,
Giulio Cesare
On 10/1/07, Michael Gentry <blacknex..mail.com> wrote:
> Have you vacuumed the original (slow) table?
>
> /dev/mrg
>
> On 10/1/07, Giulio Cesare Solaroli <giulio.cesar..mail.com> wrote:
> > Hello everybody,
> >
> > today I have being able to do some more tests and I have found out
> > that the problem seems to be caused by a "fragmentation" of the data
> > on the Postgresql table space.
> >
> > I have created a copy of the table where delete statements where very
> > slow (using the "create table .... as select from ..." syntax) and
> > matching the structure of the new copy to the original one (index and
> > constraint wise); in this new table the performance of the delete
> > statements where from 20 to 100 times faster that in the original
> > table. :-(
> >
> > This rules out Cayenne as the culprit, but leave me wondering how to
> > avoid this degradation of performances on Postgresql; but this is
> > probably not the right place where to start.
> >
> > Thank you everybody for your attention and for the very useful
> > suggestions or pointers that greatly helped me in understanding this
> > problem.
> >
> > Best regards,
> >
> > Giulio Cesare
> >
> >
> >
> >
> >
> >
> >
> > On 9/23/07, Giulio Cesare Solaroli <giulio.cesar..mail.com> wrote:
> > > Hello,
> > >
> > > I have collected a few more data, as suggested by Aristedes.
> > >
> > > On 9/23/07, Giulio Cesare Solaroli <giulio.cesar..mail.com> wrote:
> > > > On 9/23/07, Aristedes Maniatis <ar..aniatis.org> wrote:
> > > > >
> > > > > On 23/09/2007, at 5:38 PM, Giulio Cesare Solaroli wrote:
> > > > >
> > > > > > log4j.logger.org.apache.cayenne=ERROR
> > > > > > log4j.logger.org.apache.cayenne.access.QueryLogger=DEBUG
> > > > > >
> > > > > >
> > > > > > Is there anything going on on the Cayenne code between the last [batch
> > > > > > bind:xxx] log and the "updated" log?
> > > > >
> > > > > Well, you could always try:
> > > > >
> > > > > log4j.logger.org.apache.cayenne=DEBUG
> > > >
> > > > Argh. I should have thought about this myself. :-(
> > >
> > > Even with full log enabled I got the same exact log, so it looks like
> > > all the time is really spent on the DB. And the next logs confirm
> > > this.
> > >
> > >
> > > > > > Is all this time spent on the DB only?
> > > > >
> > > > > What does turning on log_min_duration_statement tell you?
> > >
> > > I have being able to run PostgreSQL with logging enabled only on my
> > > Parallels instance, as I can not start/stop the db on the deployment
> > > server; this will make the absolute times not that relevant, but I
> > > hope we can understand something more anyway.
> > >
> > > First of all, there is a huge difference between the deletion time of
> > > the "cascade" records in different tables.
> > >
> > > [...]
> > > LOG: duration: 0.020 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM connection.USRCNNRQS WHERE ID_USRCNNRQS = $1]
> > > LOG: duration: 0.021 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM connection.USRCNNRQS WHERE ID_USRCNNRQS = $1]
> > > LOG: duration: 0.020 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM connection.USRCNNRQS WHERE ID_USRCNNRQS = $1]
> > > [...]
> > >
> > > To delete rows on the USRCNNRQS (aka UserConnectionRequest) table, it
> > > averages at bout 0.020 ms.
> > >
> > >
> > > For another table (USRCNN aka UserConnection) the times range from
> > > 0.145 to 0.060, for later settling for 0.040 ms:
> > >
> > > [...]
> > > LOG: duration: 0.090 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM connection.USRCNN WHERE ID_USRCNN = $1]
> > > LOG: duration: 0.071 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM connection.USRCNN WHERE ID_USRCNN = $1]
> > > LOG: duration: 0.067 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM connection.USRCNN WHERE ID_USRCNN = $1]
> > > [...]
> > >
> > >
> > > It later took 43 seconds (!!) to parse and execute the deletion of a
> > > single record, ...
> > > [...]
> > > LOG: statement: PREPARE S_5 AS DELETE FROM clipperz.RCR WHERE ID_RCR = $1
> > > LOG: statement: <BIND>
> > > LOG: statement: EXECUTE <unnamed> [PREPARE: DELETE FROM
> > > clipperz.RCR WHERE ID_RCR = $1]
> > > LOG: duration: 42.998 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM clipperz.RCR WHERE ID_RCR = $1]
> > > LOG: statement: <BIND>
> > > LOG: statement: EXECUTE <unnamed> [PREPARE: DELETE FROM
> > > clipperz.RCR WHERE ID_RCR = $1]
> > > [...]
> > >
> > > ...later spotting time as low as 0.042 for the execution of the same query:
> > > [...]
> > > LOG: duration: 0.042 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM clipperz.RCR WHERE ID_RCR = $1]
> > > LOG: statement: <BIND>
> > > LOG: statement: EXECUTE <unnamed> [PREPARE: DELETE FROM
> > > clipperz.RCR WHERE ID_RCR = $1]
> > > [...]
> > >
> > > But as I may understand this different timing may be due to the
> > > interaction of the Virtual machine with the real server, what is
> > > puzzling me is that the deletion from the latest table had a
> > > "constant" time of about 2 seconds each:
> > > [...]
> > > LOG: duration: 1929.043 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM clipperz.RCRVRS WHERE ID_RCRVRS = $1]
> > > LOG: duration: 1991.311 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM clipperz.RCRVRS WHERE ID_RCRVRS = $1]
> > > LOG: duration: 2078.249 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM clipperz.RCRVRS WHERE ID_RCRVRS = $1]
> > > LOG: duration: 2015.047 ms statement: EXECUTE <unnamed> [PREPARE:
> > > DELETE FROM clipperz.RCRVRS WHERE ID_RCRVRS = $1]
> > > [...]
> > >
> > >
> > > If nobody as something else to suggest, I will try to get back the the
> > > DB schema to see if there is some constraint/index that is slowing
> > > down the deletion of these records.
> > >
> > > Thank you very much for your attention.
> > >
> > > Best regards,
> > >
> > > Giulio Cesare
> > >
> >
>
This archive was generated by hypermail 2.0.0 : Mon Oct 01 2007 - 13:05:42 EDT