Re: [HACKERS] CurTransactionContext freed before transaction COMMIT ???

Hello people,             We are implementing in-memory index. As a part of that, during index callbacks, under CurTransactionContext, we cache all the DMLs of a transaction in dlist(postgres's doubly linked list).             We registered transaction callback, and in transaction pre-commit event(XACT_EVENT_PRE_COMMIT), we iterate through all cached DMLs(dlist) and populate in my in-memory data structure.            --> For detailed explanation of our implementation, please look into below thread.                https://www.postgresql.org/message-id/15f4ea99b34.e69a4e1b633.8937474039794097334%40zohocorp.com            --> It was working fine until I was greeted with a segmentation fault while accessing dlist!                        --> On further examining I found that dlist head is not NULL and it is pointing to some address, but the container I extracted is pointing to 0x7f7f7f7f7f7f7f5f, and I was not able to access any members in my container.            --> https://wiki.postgresql.org/wiki/Developer_FAQ#Why_are_my_variables_full_of_0x7f_bytes.3F             From the above wiki, we came to a conclusion that the memory context in which that dlist was present was freed.             And yes CLOBBER_FREED_MEMORY is enabled by passing --enable-cassert to enable asserts in my code.            --> Normally the memory context inside XACT_EVENT_PRE_COMMIT is TopTransactionContext but in this particular case, the memory context was 'MessageContext'. Little unusual! Not sure why!            --> So basically CurTransactionContext shouldn't get freed before transaction COMMIT.            --> So what has actually happened here??? Kindly help us with your insights!