Re: COPY FREEZE has no warning

On Sat, Feb  2, 2013 at 12:09:05PM -0500, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Well, so you are saying that there really isn't any use-visible logic
> > for those messages to be different,
>
> No, and in fact the whole block of code is badly written because it
> conflates two unrelated tests.  I guess somebody was trying to save
> a couple of nanoseconds by not calling GetCurrentSubTransactionId
> if a previous test had failed, but really why should we care about
> that number of cycles in COPY preliminaries?  The code ought to be
> more like this:
>
>     /* comment about skipping FSM or WAL here */
>     if (cstate->rel->rd_createSubid != InvalidSubTransactionId ||
>         cstate->rel->rd_newRelfilenodeSubid != InvalidSubTransactionId)
>     {
>         hi_options |= HEAP_INSERT_SKIP_FSM;
>         if (!XLogIsNeeded())
>             hi_options |= HEAP_INSERT_SKIP_WAL;
>     }
>     /* comment about when we can perform FREEZE here */
>     if (cstate->freeze)
>     {
>         if (!ThereAreNoPriorRegisteredSnapshots() || !ThereAreNoReadyPortals())
>             ereport(ERROR,
>                     (ERRCODE_INVALID_TRANSACTION_STATE,
>                     errmsg("cannot perform FREEZE because of prior transaction activity")));
>
>         if (cstate->rel->rd_createSubid != GetCurrentSubTransactionId() &&
>             cstate->rel->rd_newRelfilenodeSubid != GetCurrentSubTransactionId())
>                 ereport(ERROR,
>                         (ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE,
>                         errmsg("cannot perform FREEZE because the table was not created or truncated in the current
subtransaction")));
>         hi_options |= HEAP_INSERT_FROZEN;
>     }

Yes, I found the blocking odd too --- the test for
InvalidSubTransactionId is used by hi_options, and for freeze checking.
I assumed "!= InvalidSubTransactionId" and "!=
GetCurrentSubTransactionId()" had different meanings for freeze
checking.

I compounded the problem because originally there was no FREEZE failure
so no action was taken if "!= InvalidSubTransactionId".

Applied patch attached.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +