Method snapshotState

src/jrd/tpc.cpp:674–719

}

CommitNumber TipCache::snapshotState(thread_db* tdbb, TraNumber number)
{
	// Can only be called on initialized TipCache
	fb_assert(m_tpcHeader);

	// Get data from cache
	CommitNumber stateCn = cacheState(number);

	// Transaction is committed or dead?
	if (stateCn == CN_DEAD || (stateCn >= CN_PREHISTORIC && stateCn <= CN_MAX_NUMBER))
		return stateCn;

	// We excluded all other cases above
	fb_assert(stateCn == CN_ACTIVE || stateCn == CN_LIMBO);

	// Query lock data for a transaction; if we can then we know it is still active.
	//
	// This logic differs from original TPC implementation as follows:
	// 1. We use read_data instead of taking a lock, to avoid possible race conditions
	//    (they were probably not causing much harm, but consistency is a good thing)
	// 2. Old TPC returned tra_active for transactions in limbo, which was not correct
	//
	// hvlad: tra_active is correct here as it allows caller to wait for prepared but
	// still active transaction
	Lock temp_lock(tdbb, sizeof(TraNumber), LCK_tra);
	temp_lock.setKey(number);

	if (LCK_read_data(tdbb, &temp_lock))
		return CN_ACTIVE;

	// Go to disk, and obtain state of our transaction from TIP
	int state = TRA_fetch_state(tdbb, number);

	// We already know for sure that this transaction cannot be active, so mark it dead now
	// to avoid more work in the future
	if (state == tra_active)
	{
		REPL_trans_cleanup(tdbb, number);
		TRA_set_state(tdbb, 0, number, tra_dead); // This will update TIP cache
		return CN_DEAD;
	}

	// Update cache and return new state
	stateCn = setState(number, state);
	return stateCn;
}

void TipCache::updateOldestTransaction(thread_db *tdbb, TraNumber oldest, TraNumber oldestSnapshot)
{