Re: BUG #17994: Invalidating relcache corrupts tupDesc inside ExecEvalFieldStoreDeForm()

On 2023-08-21 Mo 08:33, Alvaro Herrera wrote:
> Hello,
>
> On 2023-Jul-12, Andrew Dunstan wrote:
>
>> + entry = hash_search(missing_cache, &key, HASH_ENTER, &found);
>> +
>> + if (!found)
>> + {
>> + /* cache miss, so we need a non-transient copy of the datum */
>> + oldctx = MemoryContextSwitchTo(TopMemoryContext);
>> + entry->value =
>> + datumCopy(attrmiss->am_value, false, att->attlen);
>> + MemoryContextSwitchTo(oldctx);
>> + }
> Hmm ... when exactly do these values get freed if no longer needed? Is
> the theory that leaking them is not relevant?

Not sure I understand "relevant" here. They don't get freed. There will
be at most one entry per row in pg_attribute where atthasmissing is
true. I originally suggested cleaning them up at transaction end, but
there was an argument that that might not make them sufficiently
long-lived, and I don't know of any time more coarse grained when we can
conveniently clean them up.

cheers

andrew

--
Andrew Dunstan
EDB:https://www.enterprisedb.com