Re: Gin indexes on intarray is fast when value in array does not exists, and slow, when value exists

I wrote:
> Seems like your problem here is that the planner has no idea about the
> selectivity of this condition --- if it did, I think it would have
> made the right choice, because it would have made a much higher estimate
> for the cost of the indexscan.

> AFAICT, Postgres 9.5 does make a reasonably correct guess when given
> up-to-date stats.  I speculate that you need to ANALYZE this table.

Hmmm ... actually, I wonder if maybe '@>' here is the contrib/intarray
operator not the core operator?  The intarray operator didn't get plugged
into any real estimation logic until 9.6.

            regards, tom lane