Re: [DOCS] Documentation of pg_badkend_pid and stats functions

2007-05-06 Thread Jim Nasby

On Apr 12, 2007, at 7:54 AM, Jim Nasby wrote:
Two questions: Why is pg_backend_pid documented with the stats  
functions (9.19 System Information Functions) seems more logical.


Also, I can see mentioning the stats functions in the monitoring  
section, but shouldn't they actually be documented in with the rest  
of the functions?


No comments? Does that mean if I write up a patch it'll be accepted?
--
Jim Nasby[EMAIL PROTECTED]
EnterpriseDB  http://enterprisedb.com  512.569.9461 (cell)



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Re: [DOCS] Documentation of pg_badkend_pid and stats functions

2007-05-06 Thread Bruce Momjian
Jim Nasby wrote:
> On Apr 12, 2007, at 7:54 AM, Jim Nasby wrote:
> > Two questions: Why is pg_backend_pid documented with the stats  
> > functions (9.19 System Information Functions) seems more logical.
> >
> > Also, I can see mentioning the stats functions in the monitoring  
> > section, but shouldn't they actually be documented in with the rest  
> > of the functions?
> 
> No comments? Does that mean if I write up a patch it'll be accepted?

Yea, I was wondering about that.  I think the best idea would be to
reference the backend functions from the main functions page, rather
than move them.

-- 
  Bruce Momjian  <[EMAIL PROTECTED]>  http://momjian.us
  EnterpriseDB   http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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Re: [DOCS] row-level stats and last analyze time

2007-05-06 Thread Tom Lane
Neil Conway <[EMAIL PROTECTED]> writes:
> On Thu, 2007-26-04 at 18:07 -0400, Neil Conway wrote:
>> (1) I believe the reasoning for Tom's earlier change was not to reduce
>> the I/O between the backend and the pgstat process [...]

> Tom, any comments on this? Your change introduced an undocumented
> regression into 8.2. I think you're on the hook for a documentation
> update at the very least, if not a revert.

The documentation update seems the most prudent thing to me.  The
problem with the prior behavior is that it guarantees that every table
in the database will eventually have a pg_stat entry, even if
stats_row_level and stats_block_level are both off.  In a DB with lots
of tables that creates a significant overhead *for a feature the DBA
probably thinks is turned off*.  This is not how it worked before 8.2,
and so 8.2.0's behavior is arguably a performance regression compared
to 8.1 and before.

Now this patch went in before we realized that 8.2.x had a bug in
computing the stats-file-update delay, and it could be that after fixing
that the problem is not so pressing.  But I don't particularly care for
new features that impose a performance penalty on those who aren't using
them, and that's exactly what last_vacuum/last_analyze tracking does if
we allow it to bloat the stats file in the default configuration.

The long-term answer of course is to devise a more efficient stats
reporting scheme, but I'm not sure offhand what that would look like.

regards, tom lane

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