Re: Performance of full outer join in 8.3

Grzegorz Jaśkiewicz wrote:
> set work_mem=24000; before running the query.
>
> postgres is doing merge and sort on disc, that's always slow.
>
Ok, but why is the plan different in 8.2? As you can see the same query
is really fast in 8.2, but slow in 8.3.
> is there an index on column isin ?
>
There is a separate index on the isin column of the attachment_isins
table (attachment_isins_isin_idx). The other table (rec_isins) has the
combination of attachment and isin as primary key which creates an
implicit index. Can this index be used for the single column isin? And
again: Why doesn't this matter in 8.2??

Regards,
Christian

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