On Wed, Mar 16, 2016 at 6:53 AM, Andreas Joseph Krogh <andreas@visena.com> wrote:
På onsdag 16. mars 2016 kl. 14:37:27, skrev Tom Lane <tgl@sss.pgh.pa.us>:
Andreas Joseph Krogh <andreas@visena.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.
Please, find bitmap filtering patch, which we developed several months ago, but failed to find good use case :( Teodor is here now, so he could answer the questions.