Function TRA_sweep

src/jrd/tra.cpp:1833–1963

void TRA_sweep(thread_db* tdbb)
{
/**************************************
 *
 *	T R A _ s w e e p
 *
 **************************************
 *
 * Functional description
 *	Make a garbage collection pass thru database.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* const dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	dbb->initiateSweepRun(tdbb);

	fb_assert(dbb->dbb_flags & DBB_sweep_in_progress);

	Jrd::Attachment* const attachment = tdbb->getAttachment();

	jrd_tra* const tdbb_old_trans = tdbb->getTransaction();

	jrd_tra* transaction = NULL;

	// Clean up the temporary locks we've gotten in case anything goes wrong

	try {

		// Identify ourselves as a sweeper thread. This accomplishes two goals:
		// 1) Sweep transaction is started "precommitted" and
		// 2) Execution is throttled in JRD_reschedule() by
		// yielding the processor when our quantum expires.

		ThreadSweepGuard sweepGuard(tdbb);

		TraceSweepEvent traceSweep(tdbb);

		// Start a transaction, if necessary, to perform the sweep.
		// Save the transaction's oldest snapshot as it is refreshed
		// during the course of the database sweep. Since it is used
		// below to advance the OIT we must save it before it changes.

		transaction = TRA_start(tdbb, sizeof(sweep_tpb), sweep_tpb);

		TraNumber transaction_oldest_active = transaction->tra_oldest_active;
		tdbb->setTransaction(transaction);

		// The garbage collector runs asynchronously with respect to
		// our database sweep. This isn't good enough since we must
		// be absolutely certain that all dead transactions have been
		// swept from the database before advancing the OIT. Turn off
		// the "notify garbage collector" flag for the attachment and
		// synchronously perform the garbage collection ourselves.

		attachment->att_flags &= ~ATT_notify_gc;