Re: cache lookup failed for collation 0

Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com> writes:
> Following test-sequence causing an error "cache lookup failed for collation 0";
> postgres:5432 [42106]=# create table foobar(a bytea primary key, b int);
> CREATE TABLE
> postgres:5432 [42106]=# insert into foobar
> values('\x4c835521685c46ee827ab83d376cf028', 1);
> INSERT 0 1
> postgres:5432 [42106]=# select * from foobar where a like '%1%';
> ERROR: cache lookup failed for collation 0

Good catch!

> The error is coming from get_collation_isdeterministic() when colloid
> passed is 0. I think like we do in get_collation_name(), we should return
> false here when such collation oid does not exist.

Considering that e.g. lc_ctype_is_c() doesn't fail for InvalidOid, I agree
that it's probably a bad idea for get_collation_isdeterministic to fail.
There's a lot of code that thinks it can check for InvalidOid only in slow
paths. However, I'd kind of expect the default result to be "true" not
"false". Doing what you suggest would make match_pattern_prefix fail
entirely, unless we also put a special case there.

regards, tom lane