Re: Shouldn't non-MULTIBYTE backend refuse to start in MB database?

Tom Lane writes:

> Oh, I see. So the question still remains: can a MULTIBYTE-aware backend
> ever use a sort order different from strcmp() order? (That is, not as
> a result of LOCALE, but just because of the non-SQL-ASCII encoding.)

According to the code, no, because varstr_cmp() doesn't pay attention to
the multibyte status. Presumably strcmp() and strcoll() don't either.

> Actually there are more complicated cases that would depend on more
> features of the encoding than just sort order. Consider
>
> CREATE INDEX fooi ON foo (upper(field1));
>
> Operations involving this index will misbehave if the behavior of
> upper() ever differs between MULTIBYTE-aware and non-MULTIBYTE-aware
> code. That seems pretty likely for encodings like LATIN2...

Of course in the most general case this is a problem, because a function
can be implemented totally differently depending on any old #ifdef or
other external factors.

If the multibyte users think this check is okay, then I don't mind, since
it's usually what the users would want anyway. I'm just pointing out the
technical issues.

--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/