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Re: Problems with pg_dump

From: Stefan Holzheu <stefan(dot)holzheu(at)bitoek(dot)uni-bayreuth(dot)de>
To:
Cc: ADMIN <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Problems with pg_dump
Date: 2004-02-25 07:58:03
Message-ID: 403C558B.3040502@bitoek.uni-bayreuth.de (view raw or flat)
Thread:
Lists: pgsql-admin
> 
> pg_dump: lost synchronization with server: got message type "4", length 
> 858863113
> pg_dump: SQL command to dump the contents of table "aggr_max_hour" 
> failed: PQendcopy() failed.
> pg_dump: Error message from server: lost synchronization with server: 
> got message type "4", length 858863113
> pg_dump: The command was: COPY messungen.aggr_max_hour (id, von, wert, 
> counts) TO stdout;
> 
>>
>>> However, the error occurs only on that kind of aggregation tables. 
>>> There is a cron-job keeping the tables up to date, starting all 10 
>>> minutes. The job does delete and inserts on the table. Could this 
>>> somehow block the dump process? Normally it should not?
>>
>>
>>
>> It's hard to see how another backend would have anything to do with
>> this, unless perhaps the error is dependent on a particular data value
>> that is sometimes present in the table and sometimes not.  It looks to
>> me like either libpq or the backend is miscounting the number of data
>> bytes in the COPY datastream.  Would it be possible for you to use a
>> packet sniffer to capture the communication between pg_dump and the
>> backend?  If we could look at exactly what's going over the wire, it
>> would help to pin down the blame.
>>
> Well, I never used a packet sniffer but if anyone tells me what to 
> capture, I'd be glad to.
> 
In order to capture the pg_dump traffic with tcpdump we changed the 
pg_dump command from
pg_dump DB > ...
to
pg_dump -h 127.0.0.2 DB > ...
Since that time the dump completed without any errors. Before using 
local connection pg_dump failed to about 50%.

Anyway, we can live with that solution. But still I'd be curious to know 
what is the problem with local connections. Is there a way to capture 
traffic of local socket connections?


Stefan




-- 
-----------------------------
Dr. Stefan Holzheu
Tel.: 0921/55-5720
Fax.: 0921/55-5799
BITOeK Wiss. Sekretariat
Universitaet Bayreuth
D-95440 Bayreuth
-----------------------------

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Subject: Re: Problems with pg_dump
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