Re: GIN improvements part 1: additional information

On 12/17/2013 12:49 AM, Heikki Linnakangas wrote:
> On 12/17/2013 12:22 AM, Alexander Korotkov wrote:
>> On Mon, Dec 16, 2013 at 3:30 PM, Heikki Linnakangas
>> <hlinnakangas(at)vmware(dot)com
>>> wrote:
>>
>>> On 12/12/2013 06:44 PM, Alexander Korotkov wrote:
>>>
>>> When values are packed into small groups, we have to either insert
>>>> inefficiently encoded value or re-encode whole right part of values.
>>>
>>> It would probably be simplest to store newly inserted items
>>> uncompressed,
>>> in a separate area in the page. For example, grow the list of
>>> uncompressed
>>> items downwards from pg_upper, and the compressed items upwards from
>>> pg_lower. When the page fills up, re-encode the whole page.
>
> I hacked together an implementation of a variant of Simple9, to see how
> it performs. Insertions are handled per the above scheme.

Here's an updated version of that, using the page layout without
item-indexes that I described in the other post. This is much less buggy
than that earlier crude version I posted - and unfortunately it doesn't
compress as well. The earlier version lost some items :-(.

Nevertheless, I think this page layout and code formatting is better,
even if we switch the encoding back to the varbyte encoding in the end.

I haven't tested WAL replay or VACUUM with this version yet, so those
are likely broken.

- Heikki