Function get_undo_data

src/jrd/vio.cpp:5563–5638

static UndoDataRet get_undo_data(thread_db* tdbb, jrd_tra* transaction,
								 record_param* rpb, MemoryPool* pool)
/**********************************************************
 *
 *  g e t _ u n d o _ d a t a
 *
 **********************************************************
 *
 * This is helper routine for the VIO_chase_record_version. It is used to make
 * cursor stable - i.e. cursor should ignore changes made to the record by the
 * inner code. Of course, it is called only when primary record version was
 * created by current transaction:
 *	rpb->rpb_transaction_nr == transaction->tra_number.
 *
 * Possible cases and actions:
 *
 * - If record was not changed under current savepoint, return udNone.
 *	 VIO_chase_record_version should continue own processing.
 *
 * If record was changed under current savepoint, we should read its previous
 * version:
 *
 * - If previous version data is present at undo-log (after update_in_place,
 *	 for ex.), copy it into rpb and return udExists.
 *	 VIO_chase_record_version should return true.
 *
 * - If record was inserted or updated and then deleted under current savepoint
 *	 we should undo two last actions (delete and insert\update), therefore return
 *	 udForceTwice.
 *	 VIO_chase_record_version should continue and read second available back
 *	 version from disk.
 *
 * - Else we need to undo just a last action, so return udForceBack.
 *	 VIO_chase_record_version should continue and read first available back
 *	 version from disk.
 *
 * If record version was restored from undo log mark rpb with RPB_s_undo_data
 * to let caller know that data page is already released.
 *
 **********************************************************/
{
	if (!transaction->tra_save_point)
		return udNone;

	VerbAction* const action = transaction->tra_save_point->getAction(rpb->rpb_relation);

	if (action)
	{
		const SINT64 recno = rpb->rpb_number.getValue();
		if (!RecordBitmap::test(action->vct_records, recno))
			return udNone;

		rpb->rpb_runtime_flags |= RPB_undo_read;
		if (rpb->rpb_flags & rpb_deleted)
			rpb->rpb_runtime_flags |= RPB_undo_deleted;

		if (!action->vct_undo || !action->vct_undo->locate(recno))
			return udForceBack;