The attached patch is a new version based on v3(not including Andrei's the test case). There is no need to call datumCopy when
isnull is true.
I have not added a new runtime memoryContext so far. Continue to use mstate->tableContext, I'm not sure the memory used of probeslot will affect mstate->mem_limit.
Maybe adding a new memoryContext is better. I think I should spend a little time to learn nodeMemoize.c more deeply.
On 26/2/2024 18:34, Richard Guo wrote: > > On Mon, Feb 26, 2024 at 3:54 PM Andrei Lepikhov > <a.lepikhov@postgrespro.ru <mailto:a.lepikhov@postgrespro.ru>> wrote: > > On 26/2/2024 12:44, Tender Wang wrote: > > Make sense. I found MemoizeState already has a MemoryContext, so > I used it. > > I update the patch. > This approach is better for me. In the next version of this patch, I > included a test case. I am still unsure about the context chosen and > the > stability of the test case. Richard, you recently fixed some Memoize > issues, could you look at this problem and patch? > > > I looked at this issue a bit. It seems to me what happens is that at > first the memory areas referenced by probeslot->tts_values[] are > allocated in the per tuple context (see prepare_probe_slot). And then > in MemoizeHash_hash, after we've calculated the hashkey, we will reset > the per tuple context. However, later in MemoizeHash_equal, we still > need to reference the values in probeslot->tts_values[], which have been > cleared. Agree > > Actually the context would always be reset in MemoizeHash_equal, for > both binary and logical mode. So I kind of wonder if it's necessary to > reset the context in MemoizeHash_hash. I can only provide one thought against this solution: what if we have a lot of unique hash values, maybe all of them? In that case, we still have a kind of 'leak' David fixed by the commit 0b053e78b5. Also, I have a segfault report of one client. As I see, it was caused by too long text column in the table slot. As I see, key value, stored in the Memoize hash table, was corrupted, and the most plain reason is this bug. Should we add a test on this bug, and what do you think about the one proposed in v3?
