Thomas Hallgren wrote:
Tom Lane wrote:
Tim Allen <[EMAIL PROTECTED]> writes:
Thomas Hallgren wrote:
The position function must look for 'ch' everywhere in the string so
there's no way it can use an index.
I think the '= 0' bit is what Chris was suggesting could be the basis
for an optimisation.
Yeah. AFAICS the transformation Chris suggested is valid. I'm really
dubious that it's worth expending planner cycles to look for it though.
LIKE is something that everybody and his brother uses, but who uses this
position()=0 locution?
regards, tom lane
The documentation says: position('om' in 'Thomas') == 3 so i assumed
that the returned index was 1-based and that a zero meant 'not found'.
If I'm wrong ,perhaps the docs need to be updated?
The docs are correct so my initial point was correct. "position('ch' in user) = 0" is
equivalent to "user NOT LIKE '%ch%'" and there's no way you can index that.
Regards,
Thomas Hallgren
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