Re: bitmap-index-scan faster than seq-scan on full-table-scan (gin index)

Jesper Krogh <jesper@krogh.cc> writes:
> Conceptually searching for the "full dataset" would always be fastest
> solved by a seq-scan. The query planner enforces this so much, so not
> even "enable_seqscan=off" can convince it to to something else.
> ...
> Would it be possible to implement the "Filtering" using the gin-index and
> a subsequent visibillity-check as on the index-scan?

You're failing to make any sense whatsoever.  If you're reading the full
dataset, there is no filter condition.  If there is a potentially
indexable filter condition, the planner will certainly consider that.

Personally I think the issue here has got more to do with the
non-immutability of the single-argument form of to_tsquery, which means
it gets re-evaluated at every row during a seqscan.  Do your results
change if you work with to_tsquery('english', ...)  (or whatever your
default TS config is)?
        regards, tom lane