On Sat, Mar 19, 2016 at 5:44 AM, Jeff Janes <jeff.janes@xxxxxxxxx> wrote:
On Wed, Mar 16, 2016 at 6:53 AM, Andreas Joseph Krogh <andreas@xxxxxxxxxx> wrote:På onsdag 16. mars 2016 kl. 14:37:27, skrev Tom Lane <tgl@xxxxxxxxxxxxx>:Andreas Joseph Krogh <andreas@xxxxxxxxxx> 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 laneSo 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.
Cheers,Jeff
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