PostgreSql phraseto_tsquery is very slow - postgresql

Question

I am using PostgreSql 9.6
I have a database table with about 16 million records. I have a jsonb column - logentry -that has a field called "message". It has a GIN index created as so:
CREATE INDEX inettklog_ix_ts_message
ON public.inettklog USING gin
(to_tsvector('english'::regconfig, logentry ->> 'message'::text))
TABLESPACE pg_default;
I want to do a search for "application name".
A query with the WHERE clause
to_tsvector('english', logentry->>'message') ## plainto_tsquery('application name')
executes in 113 msecs and returns 7349 rows
EXPLAIN ANALYZE:
WindowAgg (cost=1812.98..2240.22 rows=95 width=12) (actual time=84.037..84.986 rows=7315 loops=1)
-> Bitmap Heap Scan on inettklog (cost=1812.98..2239.03 rows=95 width=4) (actual time=17.943..81.708 rows=7315 loops=1)
Recheck Cond: (to_tsvector('english'::regconfig, (logentry ->> 'message'::text)) ## plainto_tsquery('application name'::text))
Heap Blocks: exact=7574
-> Bitmap Index Scan on inettklog_ix_ts_message (cost=0.00..1812.96 rows=95 width=0) (actual time=8.542..8.542 rows=8009 loops=1)
Index Cond: (to_tsvector('english'::regconfig, (logentry ->> 'message'::text)) ## plainto_tsquery('application name'::text))
Planning time: 0.387 ms
Execution time: 85.243 ms
But I don't want "application" and "name", I want "application name"
But a query with a WHERE clause of
to_tsvector('english', logentry->>'message') ## phraseto_tsquery('application name')
takes over 2 minutes to run!
EXPLAIN ANALYZE:
WindowAgg (cost=852.98..1280.22 rows=95 width=12) (actual time=145065.204..145066.127 rows=7314 loops=1)
-> Bitmap Heap Scan on inettklog (cost=852.98..1279.03 rows=95 width=4) (actual time=55.180..145030.148 rows=7314 loops=1)
Recheck Cond: (to_tsvector('english'::regconfig, (logentry ->> 'message'::text)) ## phraseto_tsquery('application name'::text))
Heap Blocks: exact=7573
-> Bitmap Index Scan on inettklog_ix_ts_message (cost=0.00..852.96 rows=95 width=0) (actual time=8.196..8.196 rows=8008 loops=1)
Index Cond: (to_tsvector('english'::regconfig, (logentry ->> 'message'::text)) ## phraseto_tsquery('application name'::text))
Planning time: 25.926 ms
Execution time: 145067.052 ms
Surely the "<->" operator works by first locating the rows containing "application" and "name" and then filters the result to find those rows where "name" follows "application".
And, if so, why does it take 2 minutes to run???

Answer 1

The GIN index, unfortunately, cannot support ordering of the lexemes. Your first query is so much faster because it's able to handle everything using the index you built. With the phrase version, the recheck has to actually go to your table and create the ts_vectors to find the order.
You may be able to use a RUM index: https://github.com/postgrespro/rum which does include the ordering information.
This article expands on these points greatly.