Re: BUG #15892: URGENT: Using an ICU collation in a primary key column breaks ILIKE query

Arthur Zakirov <a(dot)zakirov(at)postgrespro(dot)ru> writes:
> On 04.07.2019 19:50, Daniel Verite wrote:
>> Yes. It is because of the index that the code checks if the ILIKE
>> can be evaluated with an index lookup. Otherwise it doesn't.
>> If you feel like recompiling with a temporary fix against v11.4 to do
>> your own tests, please try the attached patch.

> Also this patch works. I thinks we need to use some ICU function to
> check whether a char is a letter.

This topic seems to have slipped through the cracks, which is too bad
because we surely could have gotten it fixed in time for last week's
releases. Oh well.

I think Daniel's patch leaves more on the table than it needs to,
and I don't like Arthur's patch because it's assuming more than it
should about whether it's okay to pass a "char" to u_isalpha().
I propose that we do things as attached, instead.

(I also added a regression test case.)

regards, tom lane