"David G. Johnston" <david.g.johns...@gmail.com> writes: > On Tue, Feb 15, 2022 at 11:17 AM PG Doc comments form < > nore...@postgresql.org> wrote: >> ==> up to here, this seems pretty enough to conclude that POSITION() >> doesn't >> care at all about COLLATION and always perform a byte search.
> How collations behave is documented, in particular: > "A collation is either deterministic or nondeterministic. A deterministic > collation uses deterministic comparisons, which means that it considers > strings to be equal only if they consist of the same byte sequence." Right. POSITION does indeed do bytewise search, which is a legal implementation for any deterministic collation, but perhaps not for a nondeterministic one. Thus, it throws a feature-not-supported error if asked to use a nondeterministic collation. As you say, this is far from the only function that acts that way. regards, tom lane