Re: FETCH FIRST clause PERCENT option - Mailing list pgsql-hackers

On 1/9/19 4:43 PM, Surafel Temesgen wrote:
> 
> 
> On Wed, Jan 9, 2019 at 5:38 PM Tomas Vondra
> <tomas.vondra@2ndquadrant.com <mailto:tomas.vondra@2ndquadrant.com>> wrote:
> 
> 
>     It's hard to say what exactly are you doing, because you haven't shared
>     any code nor examples. 
> 
> 
> okay i attach in progress patch
> 

Yeah, that's what I thought - the patch computes

    node->count = DatumGetInt64(100 / DatumGetFloat8(val));

and then always fetches this number of records before emitting the next
row from the tuplestore. That's wrong, as I explained before, because
the distance does change, due to rounding.

See the attached patch, which recomputes the count regularly. I don't
claim the patch is committable or that it has no other bugs, but
hopefully it shows what I meant.

FWIW you don't need to create any slots - the two already created are
enough. You certainly don't need to create the slots within a loop.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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