From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
Cc: | exclusion(at)gmail(dot)com, pgsql-bugs(at)lists(dot)postgresql(dot)org |
Subject: | Re: BUG #17056: Segmentation fault on altering the type of the foreign table column with a default |
Date: | 2021-06-10 23:11:03 |
Message-ID: | 1816295.1623366663@sss.pgh.pa.us |
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Lists: | pgsql-bugs pgsql-hackers |
Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> On 6/10/21 6:10 PM, Tom Lane wrote:
>> Hmm. The equivalent DDL on a plain table works fine, but this is
>> crashing in the code that manipulates attmissingval. I suspect some
>> confusion about whether a foreign table column should even *have*
>> attmissingval. Andrew, any thoughts?
> My initial thought would be that it should not. If the foreign table has
> rows with missing columns then it should be up to the foreign server to
> supply them transparently. We have no notion what the foreign semantics
> of missing columns are.
Yeah, that was kind of what I thought. Probably only RELKIND_RELATION
rels should ever have attmissingval; but certainly, anything without
local storage should not.
> I can take a look at a fix tomorrow. My inclination would be simply to
> skip setting attmissingval for foreign tables.
Seems like in addition to that, we'll need a defense in this specific
code to cope with the case where the foreign column already has an
attmissingval. Or maybe, the logic to not store a new one will be enough
to keep us from reaching this crash; but we need to be sure it is enough.
regards, tom lane
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