Re: GIN improvements part 1: additional information

Hi!

On Wed, Nov 20, 2013 at 9:02 PM, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com
> wrote:

> On 06.11.2013 17:36, Alvaro Herrera wrote:
>
>> Just for my own illumination, can someone explain this bit?
>>
>> + If a posting list is too large to store in-line in a key entry, a
>> posting tree
>> + is created. A posting tree is a B-tree structure, where the ItemPointer
>> is
>> + used as the key. At the leaf-level, item pointers are stored
>> compressed, in
>> + "varbyte encoding".
>>
>> I think the first ItemPointer mentioned (the key) refers to a TID
>> pointing to the index, and "item pointers stored compressed" refers to
>> the TIDs pointing to the heap (the data). Is that correct?
>>
>
> No, they both refer to TIDs pointing to the heap.
>
>
> I'm also interested in the "FIXME explain varbyte encoding" explanation
>> currently missing, if somebody can write it down ...
>>
>
> Alexander's latest version filled in that explanation (haven't read it
> myself yet)

off-list

What's your plans about GIN now? I tried to rebase packed posting lists
with head. But I found that you've changed interface of placeToPage
function. That's conflicts with packed posting lists, because
dataPlaceToPageLeaf needs not only offset number to describe place to
insert item pointer. Do you like to commit rework of handling GIN
incomplete splits before?

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