Re: Support LIKE with nondeterministic collations

On 03.05.24 15:20, Robert Haas wrote:
> On Fri, May 3, 2024 at 4:52 AM Peter Eisentraut <peter(at)eisentraut(dot)org> wrote:
>> What the implementation does is, it walks through the pattern. It sees
>> '_', so it steps over one character in the input string, which is '.'
>> here. Then we have 'foo.' left to match in the input string. Then it
>> takes from the pattern the next substring up to but not including either
>> a wildcard character or the end of the string, which is 'oo', and then
>> it checks if a prefix of the remaining input string can be found that is
>> "equal to" 'oo'. So here it would try in turn
>>
>> '' = 'oo' collate ign_punct ?
>> 'f' = 'oo' collate ign_punct ?
>> 'fo' = 'oo' collate ign_punct ?
>> 'foo' = 'oo' collate ign_punct ?
>> 'foo.' = 'oo' collate ign_punct ?
>>
>> and they all fail, so the match fails.
>
> Interesting. Does that imply that these matches are slower than normal ones?

Yes, certainly, and there is also no indexing support (other than for
exact matches).