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Re: Logging Lock Waits

From: Jim Nasby <decibel(at)decibel(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Logging Lock Waits
Date: 2007-02-02 05:20:36
Message-ID: C0EB9B91-94E9-492A-A1D8-3D299FD4EECE@decibel.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Jan 30, 2007, at 6:32 PM, Tom Lane wrote:
> "Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
>> I'm thinking to write an INFO message, so that people can choose  
>> to log
>> this and/or the SQL statement if they choose.
>> e.g. INFO: lock wait time of XXX secs has been exceeded
>
> The available timer resources are already overloaded; adding an
> independent timeout for this will complicate the code more than seems
> justified.  Perhaps you could add a LOG message whenever the
> deadlock-check code runs (and doesn't detect an error, so is about  
> to go
> back to sleep).  This would take almost no effort, and the granularity
> could still be adjusted via the deadlock check timeout.

Sybase collected performance information for a server by periodically  
checking the status of all backend processes (ie: waiting on a user  
lock, waiting on IO, internal lock, etc) and keeping counters. Having  
that information available was useful for debugging performance  
issues (unfortunately I can't provide any specific examples since it  
was years ago I played with it). I'm thinking backends could set  
flags in shared memory to indicate what they're doing and a process  
could poll that every X milliseconds and keep stats on what's going on.

But maybe that's more along the lines of the rewrite of the stats  
system that's been talked about...
--
Jim Nasby                                            jim(at)nasby(dot)net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)



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