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

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