/*
* Given a tuple we are about to delete, determine the correct value to store
* into its t_cid field.
*
* If we don't need a combo CID, *cmax is unchanged and *iscombo is set to
* FALSE. If we do need one, *cmax is replaced by a combo CID and *iscombo
* is set to TRUE.
*
* The reason this is separate from the actual HeapTupleHeaderSetCmax()
* operation is that this could fail due to out-of-memory conditions. Hence
* we need to do this before entering the critical section that actually
* changes the tuple in shared buffers.
*/
void
HeapTupleHeaderAdjustCmax(HeapTupleHeader tup,
CommandId *cmax,
bool *iscombo)
{
/*
* If we're marking a tuple deleted that was inserted by (any
* subtransaction of) our transaction, we need to use a combo command id.
* Test for HeapTupleHeaderXminCommitted() first, because it's cheaper than a
* TransactionIdIsCurrentTransactionId call.
*/
if (!HeapTupleHeaderXminCommitted(tup) &&
TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tup)))
{
CommandId cmin = HeapTupleHeaderGetCmin(tup);
*cmax = GetComboCommandId(cmin, *cmax);
*iscombo = true;
}
else
{
*iscombo = false;
}
}
/*
* Read the ComboCID state at the specified address and initialize this
* backend with the same ComboCIDs. This is only valid in a backend that
* currently has no ComboCIDs (and only makes sense if the transaction state
* is serialized and restored as well).
*/
void
RestoreComboCIDState(char *comboCIDstate)
{
int num_elements;
ComboCidKeyData *keydata;
int i;
CommandId cid;
Assert(!comboCids && !comboHash);
/* First, we retrieve the number of ComboCIDs that were serialized. */
num_elements = *(int *) comboCIDstate;
keydata = (ComboCidKeyData *) (comboCIDstate + sizeof(int));
/* Use GetComboCommandId to restore each ComboCID. */
for (i = 0; i < num_elements; i++)
{
cid = GetComboCommandId(keydata[i].cmin, keydata[i].cmax);
/* Verify that we got the expected answer. */
if (cid != i)
elog(ERROR, "unexpected command ID while restoring combo CIDs");
}
}