On Wed, 2011-08-31 at 09:33 +0800, Craig Ringer wrote:
> On the other hand, the `IN' subquery is uncorrelated needs only run
> once, where the `EXISTS' subquery is correlated and has to run once for
> every outer record.
If the EXISTS looks semantically similar to an IN (aside from NULL
semantic
On 31 Srpen 2011, 15:59, Andy Colson wrote:
> I assume:
> Buckets: 16384 Batches: 1 Memory Usage: 4531kB
>
> That means a total of 4.5 meg of ram was used for the hash, so if my
> work_mem was lower than that it would swap? (or choose a different plan?)
Why don't you try that? Just set the work
On 8/30/2011 8:33 PM, Craig Ringer wrote:
On 31/08/2011 4:30 AM, Andy Colson wrote:
Hi all,
I have read things someplace saying not exists was better than not
in... or something like that. Not sure if that was for in/exists and
not in/not exists, and for a lot of records or not.
`EXISTS' may
On 31/08/2011 4:30 AM, Andy Colson wrote:
Hi all,
I have read things someplace saying not exists was better than not
in... or something like that. Not sure if that was for in/exists and
not in/not exists, and for a lot of records or not.
`EXISTS' may perform faster than `IN', yes. Using `IN
