Cannot get query to use btree-gin index when ORDER BY

Hi all.   Using PG-9.4   I have a query which goes something like this   The
simplified schema is like this:   CREATE TABLE message( id serial PRIMARY KEY,
subject varchar NOT NULL, folder_id integer NOT NULL REFERENCES folder(id),
received timestamp not null, fts_all tsvector );   create index
message_fts_all_folder_idx ON message using gin (fts_all, folder_id);   SELECT
m.id, m.subject   FROM message m WHERE m.folder_id = 1 AND m.fts_all @@
to_tsquery('simple', 'foo') ORDER BY received DESC LIMIT 10;   ...   On my
dataset it uses an index I have on (folder_id, received DESC), then filters the
result, which is not optimal when searching in > 1million messages and the
result is large and I'm only after the first (newest) 10.   What I'd like is to
have an index like this:   create index message_fts_all_folder_idx ON message
using gin (fts_all, folder_id, received DESC);   but GIN doesn't allow ASC/DESC
modifiers.   Any hints on how to optimize this?   Thanks.   -- Andreas Joseph
Krogh CTO / Partner - Visena AS Mobile: +47 909 56 963 andreas(at)visena(dot)com
<mailto:andreas(at)visena(dot)com> www.visena.com <https://www.visena.com>
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