Re: BRIN cost estimate

On 3/26/17 7:44 AM, Emre Hasegeli wrote:
>> If we want to have a variable which stores the number of ranges, then
>> I think numRanges is better than numBlocks. I can't imagine many
>> people would disagree there.
>
> I renamed it with other two.
>
>> At the very least please write a comment to explain this in the code.
>> Right now it looks broken. If I noticed this then one day in the
>> future someone else will. If you write a comment then person of the
>> future will likely read it, and then not raise any questions about the
>> otherwise questionable code.
>
> I added a sentence about it.
>
>> I do strongly agree that the estimates need improved here. I've
>> personally had issues with bad brin estimates before, and I'd like to
>> see it improved. I think the patch is not quite complete without it
>> also considering stats on expression indexes. If you have time to go
>> do that I'd suggest you go ahead with that.
>
> I copy-pasted expression index support from btcostestimate() as well,
> and extended the regression test.
>
> I think this function can use more polishing before committing, but I
> don't know where to begin.  There are single functions for every
> access method in here.  I don't like them being in there to begin
> with.  selfuncs.s is quite long with all kinds of dependencies and
> dependents.  I think it would be better to have the access method
> selectivity estimation functions under src/access.  Maybe we should
> start doing so by moving this to src/access/brin/brin_selfuncs.c.
> What do you think?

I have marked this patch "Needs Review".

-- 
-David
david@pgmasters.net