Giovani Garcia <giovani.garcia@protonmail.com> writes:
> The issue I'm finding is that the Oid returned for a VARCHAR column is TEXTOID (25) instead of VARCHAROID (1043).
This isn't hugely surprising in general. varchar has no operations
of its own; PG treats it as sort of a domain over text. So if you
do anything at all to a varchar column, it'd be quite likely for
the column to be implicitly coerced to text within the query.
> Now, when I run the following program (simplified for brevity),
> "SELECT key FROM oid_test WHERE value = $1",
Is that the *exact* query you're issuing? I don't see anything
in that that would cause a coercion, but maybe you left out some
relevant detail.
regards, tom lane