Re: constraints in query plans

On Sun, 15 Oct 2006, Tom Lane wrote:

> Jeremy Drake <pgsql(at)jdrake(dot)com> writes:
> > CREATE TABLE test_domain (
> > fkey integer not null,
> > k integer not null,
> > x1 integer not null,
> > x2 integer,
> > mp m_or_p not null
> > );
>
> > CREATE INDEX test_domain_k_x1_x2_m ON test_domain (k, x1, x2) WHERE mp = 'm';
> > CREATE INDEX test_domain_k_x1_x2_p ON test_domain (k, x1, x2) WHERE mp = 'p';
>
> Perhaps you need a non-partial index.

I just tried that,
CREATE INDEX test_domain_k_x1_x2_mp ON test_domain (k, x1, x2, mp);

and dropped the others. That actually works properly.
jeremyd=# explain analyze select * from test_domain where k = 1255 and mp;
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on test_domain (cost=5.37..237.21 rows=66 width=17) (actual time=0.115..0.707 rows=132 loops=1)
Recheck Cond: (k = 1255)
Filter: mp
-> Bitmap Index Scan on test_domain_k_x1_x2_mp (cost=0.00..5.37 rows=66 width=0) (actual time=0.081..0.081 rows=132 loops=1)
Index Cond: ((k = 1255) AND (mp = true))
Total runtime: 1.137 ms
(6 rows)

I thought I had to refer to all of the columns in order for this to work,
that I could not skip some in the middle, but it seems to work.

--
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