Re: single transaction vs multiple transactions

Sven Geisler wrote:
> I have to refactoring a 'DELETE FROM x WHERE y IN (...)' because IN got
> to much parameters. => 'stack depth limit exceeded'
> I don't want to increase just the parameter for max_stack_depth. It is
> better to refactoring because the number of arguments to IN may increase
> in the future.
>
> My approach is to do multiple 'DELETE FROM x WHERE y=...'.

You could also do something in between, issuing the deletes in batches
of say 100 deletes each. But using a temporary table is much better.

> My question is now, what is better for PostgreSQL from a performance
> perspective?
> 1. all multiple deletes in one transaction
> 2. each delete in its own transaction

All in one transaction is definitely faster.

> The number of arguments is around 10,000.
>
> BTW: The arguments are generate in the application tier. I would have to
> create a temporary table which I can use in 'DELETE FROM x WHERE y IN
> (SELECT z FROM tmp)'.

I think that's exactly what you should do.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com