Re: Regex query not using index

a final question: why does this syntax do a seq scan + filter:

select * from tablea where fielda = fielda -or- select * from
tablea where fielda in (fielda)

while this syntax results in no filter, seq scan only

select * from tablea where 1 = 1

it seems that both where clauses should be ignored by the optimizer-
or am i missing something

On Feb 19, 2008 9:45 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> "Postgres User" <postgres(dot)developer(at)gmail(dot)com> writes:
> > Yes that works, but the whole point of the exercise is replace many OR
> > statements with 1 regex expression. So it's not what I'm looking for.
>
> Unfortunately, Postgres is not as intelligent as you are. There is
> no mechanism to rewrite a multi-branch regex condition into multiple
> indexscans. I recommend going back to the OR's.
>
> regards, tom lane
>