Eval_const_expressions() doesn't know about ScalarArrayOpExpr. We
simplify the arguments, but if all the arguments are booleans, we don't
take the obvious step of replacing the whole expression with a boolean
Const. For example:
postgres=# explain select * from foo where 1 IN (1,2,3);
QUERY PLAN
-------------------------------------------------------------
Result (cost=0.00..35.50 rows=2550 width=4)
One-Time Filter: (1 = ANY ('{1,2,3}'::integer[]))
-> Seq Scan on foo (cost=0.00..35.50 rows=2550 width=4)
(3 rows)
I would've expected that to be fully evaluated at plan-time, and
optimized away.
That seems like an oversight. I guess that scenario doesn't happen very
often in practice, but there's no reason not to do it when it does.
Patch attached.
On a side-note, I find it a bit awkward that ScalarArrayOpExpr uses a
2-element List to hold the scalar and array arguments. Wouldn't it be
much more straightforward to have explicit "Expr *scalararg" and "Expr
*arrayarg" fields?
- Heikki
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