Re: GIN improvements part 1: additional information

On 29.06.2013 11:56, Heikki Linnakangas wrote:
> On 25.06.2013 01:03, Alexander Korotkov wrote:
>> New revision of patch is attached. Now it includes some docs.
>
> Thanks! I'm looking into this in detail now.
>
> First, this patch actually contains two major things:
>
> 1. Pack item pointers more tightly on posting data leaf pages.
> 2. Allow opclass implementation to attach "additional information" to
> each item pointer.
>
> These are two very distinct features, so this patch needs to be split
> into two. I extracted the 1st part into a separate patch, attached, and
> am going to focus on that now.
>
> I made one significant change: I removed the 'freespace' field you added
> to GinpageOpaque. Instead, on data leaf pages the offset from the
> beginning of the page where the packed items end is stored in place of
> the 'maxoff' field. This allows for quick calculation of the free space,
> but there is no count of item pointers stored on the page anymore, so
> some code that looped through all the item pointers relying on 'maxoff'
> had to be changed to work with the end offset instead. I'm not 100%
> wedded on this, but I'd like to avoid adding the redundant freespace
> field on pages that don't need it, because it's confusing and you have
> to remember to keep them in sync.

Ah, crap, looks like I sent the wrong patch, and now I can't find the
correct one anymore. The patch I sent didn't include the changes store
end offset instead of freespace. I'll rewrite that part..

- Heikki