Re: Using functions as filters in queries

Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> writes:
> Of course, I misread what explain did (without trying the
> enable_seqscan=off case) and this is still not indexable because even
> after that, you'll not get a clause on the outside that it considers
> indexable. It is smart enough (7.4 anyway) to make the filter ((t.*).n)=5
> which I thought it'd index, but doesn't. :(

As of a few moments ago, CVS tip reduces that to t.n=5 which is
indexable.

regression=# EXPLAIN select * from t where f(t, 5) AND x like 'a%';
QUERY PLAN
--------------------------------------------------------------
Index Scan using ti on t (cost=0.00..17.08 rows=1 width=38)
Index Cond: (n = 5)
Filter: (x ~~ 'a%'::text)
(3 rows)

regards, tom lane