"Tom Lane" <tgl@xxxxxxxxxxxxx> wrote
>
> No, that's completely irrelevant to his problem. The reason we can't do
> this is that the transformation from "x << const" to a range check on x
> is a plan-time transformation; there's no mechanism in place to do it
> at runtime. This is not easy to fix, because the mechanism that's doing
> it is primarily intended for LIKE/regex index optimization, and in that
> case a runtime pattern might well not be optimizable at all.
>
Not quite understand, sorry ...
(1) For this query (in an as-is PG syntax, which find out all rectangles lie
in a given rectangle) :
SELECT r FROM all_rectangles
WHERE r << rectangle('(1,9),(9,1)');
If there is a GiST/Rtree index associated with all_rectangles.r, how do
optimizer estimate the cost to decide that we should use this index or
not(then by a seqscan)?
(2) Does your above explaination mean that we can't use GiST for a spatial
join operation?
Regards,
Qingqing
