Re: Searching GIN-index (FTS) and sort by timestamp-column

On Wed, Mar 16, 2016 at 6:53 AM, Andreas Joseph Krogh <andreas(at)visena(dot)com>
wrote:

> På onsdag 16. mars 2016 kl. 14:37:27, skrev Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>
> Andreas Joseph Krogh <andreas(at)visena(dot)com> writes:
> > 1. Why isnt' folder_id part of the index-cond?
>
> Because a GIN index is useless for sorting.
>
> > 2. Is there a way to make it use the (same) index to sort by
> > received_timestamp?
>
> No.
>
> > 3. Using a GIN-index, is there a way to use the index at all for sorting?
>
> No.
>
> > 4. It doesn't seem like ts_rank uses the index for sorting either.
>
> Same reason.
>
> regards, tom lane
>
>
> So it's basically impossible to use FTS/GIN with sorting on large datasets?
> Are there any plans to improve this situation?
>

I don't see why it would not be possible to create a new execution node
type that does an index scan to obtain order (or just to satisfy an
equality or range expression), and takes a bitmap (as produced by the
FTS/GIN) to apply as a filter. But, I don't know of anyone planning on
doing that.

Cheers,

Jeff