Re: pg_stat_transaction patch

Hi Takahiro,

Here is an updated version of the patch.

Thanks Magnus H for the help :)

1.4: Ported to head. Updated tests. Removed pg_stat_report.


2010/5/25 Takahiro Itagaki <itagaki.takahiro@oss.ntt.co.jp>

>
> Joel Jacobson <joel@gluefinance.com> wrote:
>
> > I applied all the changes on 9.0beta manually and then it compiled
> without
> > any assertion failures.
> >
> > I also changed the oids to a different unused range, since the ones I
> used
> > before had been taken in 9.0beta1.
>
> Thanks, but you still need to test your patch:
>
>  - You need to check your patch with "make check", because it requires
>   adjustments in "rule" test; Your pg_stat_transaction_function is the
>   longest name in the system catalog.
>
>  - You need to configure postgres with --enable-cassert to enable internal
>   varidations. The attached test case failed with the following TRAP.
> TRAP: FailedAssertion("!(entry->trans == ((void *)0))", File: "pgstat.c",
> Line: 715)
> TRAP: FailedAssertion("!(tabstat->trans == trans)", File: "pgstat.c", Line:
> 1758)
>
> > I suspect it is because get_tabstat_entry for some reason returns NULL,
> in
> > for example pg_stat_get_transaction_tuples_inserted(PG_FUNCTION_ARGS).
> >
> > Does the function look valid? If you can find the error in it, the other
> > functions probably have the same problem.
>
> For the above trap, we can see the comment:
>    /* Shouldn't have any pending transaction-dependent counts */
> We don't expect to read stats entries during transactions. I'm not sure
> whether accessing transitional stats during transaction is safe or not.
>
> We might need to go other directions, for example:
>  - Use "session stats" instead "transaction stats". You can see the same
>    information in difference of counters between before and after the
>    transaction.
>  - Export pgBufferUsage instead of relation counters. They are
>    buffer counters for all relations, but we can obviously export
>    them because they are just plain variables.
>
> Regards,
> ---
> Takahiro Itagaki
> NTT Open Source Software Center
>
>
>


-- 
Best regards,

Joel Jacobson
Glue Finance

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