Re: GIN improvements part 1: additional information

On Wed, Jan 22, 2014 at 9:28 PM, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com
> wrote:

> On 01/22/2014 02:17 PM, Alexander Korotkov wrote:
>
>> We already spent a lot of time with compression. Now we need to figure out
>> the result we want see. I spent quite long time debugging varbyte encoding
>> without segments. Finally, it passed very many tests without any problems.
>> Now, it is just piece of junk. I'm afraid that we will have to reimplement
>> everything from scratch another two or three times because code doesn't
>> look perfect. For sure, it's incompatible with getting something into 9.4.
>>
>
> That's a bit harsh :-). But yes, I understand what you're saying. It's
> quite common for large patches like this to be rewritten several times
> before being committed; you just don't know what works best until you've
> tried many designs.
>
>
> Remember we have also subsequent fast-scan which is very needed for hstore
>> and other application.
>> I propose to do final decisions now and concentrate forces on making
>> committable patch with these decisions. And don't change these decisions
>> even if somebody have idea how to improve code readability in 100 times
>> and
>> potential extendability in 1000 times.
>> I propose following decisions:
>> 1) Leave uncompressed area, allow duplicates in it
>> 2) Don't introduce Items on page.
>>
>
> Well, I got the insertions to work now without the uncompressed area, so
> in the spirit of Just Getting This Damn Patch Committed, I'm going to go
> ahead with that. We can add the uncompressed area later if performance
> testing shows it to be necessary. And I agree about the Items on page idea
> - we can come back to that too still in 9.4 timeframe if necessary, but
> probably not.
>
> So, committed. It's the same design as in the most recent patch I posted,
> but with a bunch of bugs fixed, and cleaned up all over. I'm going to move
> to the fast scan patch now, but please do test and review the committed
> version to see if I missed something.

Great! Thanks a lot!
Assertion in dataPlaceToPageLeafRecompress is too strong. Page can contain
GinDataLeafMaxContentSize bytes. Patch is attached.
My test-suite don't run correctly. I'm debugging now.

------
With best regards,
Alexander Korotkov.