On 03.06.2016 16:05, Amit Kapila wrote:
On Fri, Jun 3, 2016 at 1:34 AM, Konstantin Knizhnik
<k.knizh...@postgrespro.ru <mailto:k.knizh...@postgrespro.ru>> wrote:
We have to add three more functions to eXtensible Transaction
Manager API (XTM):
/*
* Calculate transaction state size. This method is invoked by
EstimateTransactionStateSpace to copy transaction
* state to parallel workers
*/
size_t (*GetTransactionStateSize)(void);
/*
* Serialize transaction state
*/
void (*SerializeTransactionState)(void* ctx);
/*
* Deserialize transaction state
*/
void (*DeserializeTransactionState)(void* ctx);
In above proposal, are you suggesting to change the existing API's as
well, because the parameters of function pointers don't match with
exiting API's. I think it is better to consider this along with the
overall XTM API.
Sorry, but right now I have not replaced existed functions
EstimateTransactionStateSpace/SerializeTransactionState/StartParallelWorkerTransaction
with XTM indirect calls. If was my original intention, but these
functions access static variable CurrentTransactionState defined in xact.c.
So if user-defined TM wants to override this functions, it will have to
invoke original functions to save/restore CurrentTransactionState.
It is not convenient.
This is why three XTM functions above are now called by existed xact
funcations to save additional state, for example:
Size
EstimateTransactionStateSpace(void)
{
TransactionState s;
Size nxids = 6; /* iso level, deferrable, top &
current XID,
* command counter, XID count */
for (s = CurrentTransactionState; s != NULL; s = s->parent)
{
if (TransactionIdIsValid(s->transactionId))
nxids = add_size(nxids, 1);
nxids = add_size(nxids, s->nChildXids);
}
nxids = add_size(nxids, nParallelCurrentXids);
nxids = mul_size(nxids, sizeof(TransactionId));
return add_size(nxids, TM->GetTransactionStateSize());
}
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
