Re: Allow multi-byte characters as escape in SIMILAR TO and SUBSTRING

Heikki Linnakangas <hlinnakangas(at)vmware(dot)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
similar_escape anyway?

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.

regards, tom lane