Re: Querying a table with jaccard similarity with 1.6 million records take 12 seconds

Michael Lewis <mlewis@entrata.com> writes:
> This is showing many false positives from the index scan that get removed
> when the actual values are examined. With such a long search parameter,
> that does not seem surprising. I would expect a search on "raj nagar
> ghaziabad 201017" or something like that to yield far fewer results from
> the index scan. I don't know GIN indexes super well, but I would guess that
> including words that are very common will yield false positives that get
> filtered out later.

Yeah, the huge "Rows Removed" number shows that this index is very
poorly adapted to the query.  I don't think the problem is with GIN
per se, but with a poor choice of how to use it.  The given example
looks like what the OP really wants to do is full text search.
If so, a GIN index should be fine as long as you put tsvector/tsquery
filtering in front of it.  If that's not a good characterization of
the goal, it'd help to tell us what the goal is.  (Just saying "I
want to use jaccard similarity" sounds a lot like a man whose only
tool is a hammer, therefore his problem must be a nail, despite
evidence to the contrary.)

            regards, tom lane