On 08/25/2014 06:14 PM, Tom Lane wrote:
Heikki Linnakangas <hlinnakan...@vmware.com> writes:
On 08/25/2014 04:48 PM, Tom Lane wrote:
[ scratches head... ] Surely similar_escape is marked immutable, and
will therefore be executed exactly once in either of these formulations,
because the planner will fold the expression to a constant.
Yeah, just noticed that myself..
... although, given that, it is also fair to wonder how much the speed of
similar_escape really matters. Surely in most use-cases the pattern and
escape char will be constants. And, when they are not, wouldn't the
subsequent parsing work for the regexes dominate the cost of
IOW, I'm not sure we should be advising Jeff to duplicate code in
order to have a fast path. Keeping it short might be the best goal.
It's certainly not worth bending over backwards for a small performance
gain here, but I think special-casing a single-byte escape sequence is
still quite reasonable. It doesn't make the code any longer.
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