> On Mon, 30 Aug 2004, Martin Sarsale wrote:
> > "Multicolumn indexes can only be used if the clauses involving the
> > indexed columns are joined with AND. For instance,
> >
> > SELECT name FROM test2 WHERE major = constant OR minor = constant;
>
> You can use DeMorgan's Theorem to transform an O
On Mon, 30 Aug 2004, Martin Sarsale wrote:
> "Multicolumn indexes can only be used if the clauses involving the
> indexed columns are joined with AND. For instance,
>
> SELECT name FROM test2 WHERE major = constant OR minor = constant;
You can use DeMorgan's Theorem to transform an OR clause to an
> Using a functional index you can define an index around the way you
> access the data. There is no faster or better way to do it...this is a
> mathematical truth, not a problem with the planner. Why not use the
> right tool for the job? A boolean index is super-efficient both in disk
> space
Martin Sarsale <[EMAIL PROTECTED]> writes:
> I indexed columns c and d (separately) but this query used the slow
> seqscan instead of the index scan:
> select * from t where c<>0 or d<>0;
> After playing some time, I noticed that if I change the "or" for an
> "and", pg used the fast index scan (b
Another option here is to use a partial index. You can index on some other
column -- perhaps the column you want the results ordered by where the where
clause is true.
Something like:
create index t_idx on t (name) where c>0 and d>0;
then any select with a matching where clause can use the inde
On Mon, 30 Aug 2004, Martin Sarsale wrote:
> On Mon, 2004-08-30 at 15:06, Merlin Moncure wrote:
> > create function is_somethingable (ctype, dtype) returns boolean as
>
> Thanks, but I would prefer a simpler solution.
>
> I would like to know why this uses a seqscan instead of an index scan:
>
> c
create index t_idx on t((c+d));
select * from t where c+d > 0;
Why not :
select ((select * from t where c<>0::bigint) UNION (select * from t where
d<>0::bigint))
group by whatever;
or someting ?
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TIP 3: if pos
