Re: shared memory/max_locks_per_transaction error

On Mar 17, 2008, at 9:55 AM, Tom Lane wrote:

> "Kynn Jones"  writes:
>> I'm leaning towards the re-design option, primarily because I  
>> really don't
>> really understand the consequences of cranking up  
>> max_locks_per_transaction.
>> E.g. Why is its default value 2^6, instead of, say, 2^15?  In fact,  
>> why is
>> there a ceiling on the number of locks at all?
>
> Because the size of the lock table in shared memory has to be set at
> postmaster start.
>
> There are people running DBs with a couple hundred thousand tables,
> but I don't know what sorts of performance problems they face when
> they try to run pg_dump.  I think most SQL experts would suggest
> a redesign: if you have lots of essentially identical tables the
> standard advice is to fold them all into one table with one more
> key column.

That's me!  Our dumps currently take about 36 hours but what's more  
alarming is that vanilla restore takes about 4 days.  And, yes, a  
redesign is currently in the works :)  However, for Kynn's case, I  
doubt he'll have too much trouble with 35000 tables as long as that  
number stays fairly static and his design doesn't rely on that number  
growing, which is what we currently have.

Erik Jones

DBA | Emma®
erik@myemma.com
800.595.4401 or 615.292.5888
615.292.0777 (fax)

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