[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.

           --> 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.

            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!

For your reference, a code snippet of our implementation is pasted below:

/*** Code snippet starts ***/

dlist_head DMLInfo = {{NULL, NULL}};

}

static void GraphIndex_xactCallback(XactEvent event, void *arg) 

{