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Re: Database possible corruption , unsolvable mystery

From: Mark Lewis <mark(dot)lewis(at)mir3(dot)com>
To: Eric Lauzon <eric(dot)lauzon(at)abovesecurity(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Database possible corruption , unsolvable mystery
Date: 2006-03-29 22:16:51
Message-ID: 1143670611.5634.11.camel@archimedes (view raw or flat)
Thread:
Lists: pgsql-performance
Can you post an explain analyze for the delete query?  That will at
least tell you if it is the delete itself which is slow, or a trigger /
referential integrity constraint check.  Which version of PG is this?

-- Mark Lewis

On Wed, 2006-03-29 at 12:58 -0500, Eric Lauzon wrote:
> Greetings,
> 
> 	We have an issue where we have a database with many tables.
> 	The layout of the database is 3 set of look alike tables with different names.
> 	Each set of tables has some referential integrety that point back to the main
> 	control table.
> 
> 	On two set of tables we are able to efficiently delete referential and main record
> 	without a problems, but on the 3rd set we have an issue where the control table is clugged
> 	and delete seem to take forever , as example on the first two set a delete of 60K record take about
> 	4 second to 10 second but on the 3rd set it can take as long as 3hours.
> 
> 	This seem to be only affecting one database , the schema and way of doing is replicated elsewhere
> 	and if efficient.
> 
> 	The question is, even after droping 3rd set integrity , dumping the table data , deleting the table,
> 	doing a manual checkpoint and recreating the table with the dump data , with or without referential
> 	integrity , the problems still araise.
> 
> 	If we copy the data from the live table and do a create table aaa as select * from problematic_table;
> 	the table aaa operations are normal and efficient.
> 
> 	This is why our investigation brought us to the folowing questions:
> 
> 	1. Are postgresql data file name are hashed references to table name(as oracle)? [~path to data EX:/var/log/pgsql/data/[arbitraty   			   numbers]/[datafile]]?
> 
> 	2. If the data files are corrupted and we re-create is it possible it uses the same files thus creating the same issue?
> 
>  	3. Since we know that all the tables has that problems is there an internal table with undisclosed references to tables data files?
> 	
> 	I hope the questions were clear.
> 
> 	Have a good day, and thank you in advance.
> 
> 
> Eric Lauzon
> [Recherche & Développement]
> Above Sécurité / Above Security
> Tél  : (450) 430-8166
> Fax : (450) 430-1858
> 
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