Re: Allow use of immutable functions operating on constants with constraint exclusion

"Marshall, Steve" <smarshall(at)wsi(dot)com> wrote:

> the first query would be optimized using
> constraint exclusion, while the second query would not:
>
> SELECT * FROM test_bulletins WHERE created_at > '2006-09-09
> 05:00:00+00'::timestamptz;
> SELECT * FROM test_bulletins WHERE created_at > '2006-09-09
> 05:00:00+00'::timestamptz + '0 days'::interval;

Hmmm... CE seems to be still not enough to optimize complex expressions.
If I added the wrapper function, it worked.

CREATE FUNCTION timeadd(timestamptz, interval) RETURNS timestamptz
AS $$ SELECT $1 + $2; $$ LANGUAGE sql IMMUTABLE;

SELECT * FROM test_bulletins WHERE created_at >
timeadd('2006-09-09 05:00:00+00', '0 days');

I noticed that we should be careful about CE with prepared statements
and functions. Seamless partitioning requires more works.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center