Ashutosh Sharma <ashu.coek88@gmail.com> writes:
> The issue here is that PLpgSQL_rec structure being updated by
> revalidate_rectypeid() is actually a local/duplicate copy of the
> PLpgSQL_rec structure available in plpgsql_HashTable (refer to
> copy_plpgsql_datums() where you would notice that if datum type is
> PLPGSQL_DTYPE_REC we actually mempcy() the PLpgSQL_rec structure
> available in func >datums[] array). This basically means that the
> rectypeid field updated post typcache entry validation in
> revalidation_rectypeid() is actually a field in duplicate copy of
> PLpgSQL_rec structure, not the original copy of it available in
> func->datums[]. Hence, when the same function is executed for the
> second time, the rectypeid field of PLpgSQL_rec structure being
> reloaded from the func->datums[] actually contains the stale value
> however the typcache entry in it is up-to-date which means
> revalidation_rectypeid() returns immediately leaving a stale value in
> rectypeid. This causes the function make_expanded_record_from_typeid()
> to use the outdated value in rec->rectypeid resulting into the given
> error.
Good catch!
> To fix this, I think instead of using rec->rectypeid field we should
> try using rec->datatype->typoid when calling
> make_expanded_record_from_typeid().
This is a crummy fix, though. In the first place, if we did it like this
we'd have to fix every other caller of revalidate_rectypeid() likewise.
Basically the issue here is that revalidate_rectypeid() is failing to do
what it says on the tin, and you're proposing to make the callers work
around that instead of fixing revalidate_rectypeid(). That seems like
an odd choice from here.
More generally, the reason for the separation between PLpgSQL_rec and
PLpgSQL_type in this part of the code is that PLpgSQL_rec.rectypeid is
supposed to record the actual type ID currently instantiated in that
variable (in the current function execution), whereas PLpgSQL_type is a
cache for the last type lookup we did; that's why it's okay to share the
latter but not the former across function executions. So failing to
update rec->rectypeid is almost certainly going to lead to problems
later on.
I pushed a fix that makes revalidate_rectypeid() deal with this case.
Thanks for the report and debugging!
regards, tom lane