Re: OID wraparound: summary and proposal

> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> >> For input, I see no downside to just
> >> ignoring the incoming OIDs.  For output, I can see three reasonable
> >> possibilities:
> >> 
> >> A. Pretend WITH OIDS wasn't mentioned.  This might seem to be
> >> "do the right thing", but a rather strong objection is that the
> >> app will not get back the data it was expecting.
> >> 
> >> B. Return NULLs or 0s for the OIDs column.
> >> 
> >> C. Raise an error and refuse to do the copy at all.
> >> 
> >> C is probably the most conservative answer.
> 
> > If we fail on load, we should fail on dump.  Why not fail on COPY WITH
> > OIDS on a non-oid table?
> 
> I'm confused --- I was proposing that we *not* fail on load.  What's the
> point of failing on load?

I meant to say we should fail on dump _and_ load.  If we don't we are
throwing away the oid's they are loading because though the table has no
oid column.  Seems like something that should fail.


> 
> >> How so?  pg_description is broken anyway given that we don't enforce OID
> >> uniqueness across system catalogs.  Also, in the future we could
> 
> > We have a script to detect them and the oid counter it unique. In what
> > way do we not enforce it.
> 
> In a running system, once the OID counter wraps around there's no
> guarantee that you won't have duplicate OIDs in different system
> tables.  The only enforcement mechanism we have is the unique indexes,
> and those will only check per-table.  However, that's fine --- it's
> as much as we need.  For everything except pg_description, that is.
> Since pg_description currently makes an unchecked and uncheckable
> assumption of global uniqueness of OIDs, it's broken.

If you consider random table creation failures acceptible.  In oid
wraparound, whether pg_description could point to two rows with the same
oid is the smallest part of our problem.  I think the whole idea we can
run reliably with an oid wraparound is questionable.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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