Andres Freund <and...@anarazel.de> writes: > On 2020-01-14 17:01:01 -0500, Tom Lane wrote: >> But I agree that not checking null-ness >> explicitly is kind of unsafe. We've never before had any expectation >> that the Datum value of a null is anything in particular.
> I'm still not sure I actually fully understand the bug. It's obvious how > returning the input value again could lead to memory not being freed (so > that leak seems to go all the way back). And similarly, since the > introduction of expanded objects, it can also lead to the expanded > object not being deleted. > But that's not the problem causing the crash here. What I think must > instead be the problem is that pergroupstate->transValueIsNull, but > pergroupstate->transValue is set to something looking like a > pointer. Which caused us not to datumCopy() a new transition value into > a long lived context. and then a later transition causes us to free the > short-lived value? Yeah, I was kind of wondering that too. While formally the Datum value for a null is undefined, I'm not aware offhand of any functions that wouldn't return zero --- and this would have to be an aggregate transition function doing so, which reduces the universe of candidates quite a lot. Plus there's the question of how often a transition function would return null for non-null input at all. Could we see a test case that provokes this crash, even if it doesn't do so reliably? regards, tom lane