Re: Fix for gistchoose

On Thu, Aug 30, 2012 at 4:48 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Thu, Aug 30, 2012 at 4:15 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Yeah, the idea of replacing sum_grow with a boolean just occurred to me
>>> too. As is, I think the code is making some less-than-portable
>>> assumptions about what will happen if sum_grow overflows; which can
>>> definitely happen, seeing that gistpenalty and its callees intentionally
>>> return infinity in some cases. I'd rather it didn't attempt to add
>>> column penalties together, and I think there's a case to be made that
>>> not doing so is a back-patchable bug fix.
>
>> Keep in mind that the worst case outcome is the index quality is worse
>> than it otherwise would have been, so it's not like
>> OMG-PostgreSQ-eats-your-data.
>
> Agreed, but we've seen plenty of complaining about bloated gist indexes,
> and this might be the cause.

More likely one of several, but sure.

>>> I'll take a shot at improving this some more.
>
>> Okey dokey.
>
> Attached is a revised version of gistchoose(); I've not yet transposed
> the changes into gistRelocateBuildBuffersOnSplit(). It looks a lot
> more readable to me now. Objections?

Looks good to me.

--
Robert Haas
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