Re: GIN fast insert

On Tue, Feb 24, 2009 at 10:39 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On my system this takes about 45 ms to execute with default settings
>> and about 90 ms to execute with index scan disabled.
>
> [ shrug... ]  That's well within my threshold of pain for this.
> In any case, it might be possible to buy some/all of that back with
> minor optimization effort on the bitmap-scan code paths; nobody's
> ever really bothered to profile that AFAIK.  There is no real
> difference in the useful work (page and tuple fetches) getting done
> in the two cases, so there's no reason in principle for bitmap scan
> to be much slower than indexscan here.  The LIMIT case is the only
> one I'm aware of where there's a fundamental reason that bitmap scan
> should be slower.

Uh, a semi or anti join stops as soon as one matching row is found,
doesn't it?  ISTM that a semi or anti join is in essence an iterated
limit 1 clause.

...Robert