nodemergejoin.c

关系型数据库 Postgresql 6.5.2

	outerPlan = outerPlan((Plan *) node);
	econtext = mergestate->jstate.cs_ExprContext;
	mergeclauses = node->mergeclauses;
	qual = node->join.qual;

	if (ScanDirectionIsForward(direction))
	{
		outerSkipQual = mergestate->mj_OuterSkipQual;
		innerSkipQual = mergestate->mj_InnerSkipQual;
	}
	else
	{
		outerSkipQual = mergestate->mj_InnerSkipQual;
		innerSkipQual = mergestate->mj_OuterSkipQual;
	}

	/* ----------------
	 *	ok, everything is setup.. let's go to work
	 * ----------------
	 */
	if (mergestate->jstate.cs_TupFromTlist)
	{
		TupleTableSlot *result;
		ProjectionInfo *projInfo;
		bool		isDone;

		projInfo = mergestate->jstate.cs_ProjInfo;
		result = ExecProject(projInfo, &isDone);
		if (!isDone)
			return result;
	}
	for (;;)
	{
		/* ----------------
		 *	get the current state of the join and do things accordingly.
		 *	Note: The join states are highlighted with 32-* comments for
		 *		  improved readability.
		 * ----------------
		 */
		MJ_dump(econtext, mergestate);

		switch (mergestate->mj_JoinState)
		{

				/*
				 * EXEC_MJ_INITIALIZE means that this is the first time
				 * ExecMergeJoin() has been called and so we have to
				 * initialize the inner, outer and marked tuples as well
				 * as various stuff in the expression context.
				 */
			case EXEC_MJ_INITIALIZE:
				MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE\n");

				/*
				 * Note: at this point, if either of our inner or outer
				 * tuples are nil, then the join ends immediately because
				 * we know one of the subplans is empty.
				 */
				innerTupleSlot = ExecProcNode(innerPlan, (Plan *) node);
				if (TupIsNull(innerTupleSlot))
				{
					MJ_printf("ExecMergeJoin: **** inner tuple is nil ****\n");
					return NULL;
				}

				outerTupleSlot = ExecProcNode(outerPlan, (Plan *) node);
				if (TupIsNull(outerTupleSlot))
				{
					MJ_printf("ExecMergeJoin: **** outer tuple is nil ****\n");
					return NULL;
				}

				/* ----------------
				 *	 store the inner and outer tuple in the merge state
				 * ----------------
				 */
				econtext->ecxt_innertuple = innerTupleSlot;
				econtext->ecxt_outertuple = outerTupleSlot;

				mergestate->mj_MarkedTupleSlot->ttc_tupleDescriptor =
					innerTupleSlot->ttc_tupleDescriptor;

				/* ----------------
				 *	initialize merge join state to skip inner tuples.
				 * ----------------
				 */
				mergestate->mj_JoinState = EXEC_MJ_SKIPINNER;
				break;

				/*
				 * EXEC_MJ_JOINMARK means we have just found a new outer
				 * tuple and a possible matching inner tuple. This is the
				 * case after the INITIALIZE, SKIPOUTER or SKIPINNER
				 * states.
				 */
			case EXEC_MJ_JOINMARK:
				MJ_printf("ExecMergeJoin: EXEC_MJ_JOINMARK\n");
				ExecMarkPos(innerPlan);

				MarkInnerTuple(econtext->ecxt_innertuple, mergestate);

				mergestate->mj_JoinState = EXEC_MJ_JOINTEST;
				break;

				/*
				 * EXEC_MJ_JOINTEST means we have two tuples which might
				 * satisfy the merge clause, so we test them.
				 *
				 * If they do satisfy, then we join them and move on to the
				 * next inner tuple (EXEC_MJ_JOINTUPLES).
				 *
				 * If they do not satisfy then advance to next outer tuple.
				 */
			case EXEC_MJ_JOINTEST:
				MJ_printf("ExecMergeJoin: EXEC_MJ_JOINTEST\n");

				qualResult = ExecQual((List *) mergeclauses, econtext);
				MJ_DEBUG_QUAL(mergeclauses, qualResult);

				if (qualResult)
					mergestate->mj_JoinState = EXEC_MJ_JOINTUPLES;
				else
					mergestate->mj_JoinState = EXEC_MJ_NEXTOUTER;
				break;

				/*
				 * EXEC_MJ_JOINTUPLES means we have two tuples which
				 * satisified the merge clause so we join them and then
				 * proceed to get the next inner tuple (EXEC_NEXT_INNER).
				 */
			case EXEC_MJ_JOINTUPLES:
				MJ_printf("ExecMergeJoin: EXEC_MJ_JOINTUPLES\n");
				mergestate->mj_JoinState = EXEC_MJ_NEXTINNER;

				qualResult = ExecQual((List *) qual, econtext);
				MJ_DEBUG_QUAL(qual, qualResult);

				if (qualResult)
				{
					/* ----------------
					 *	qualification succeeded.  now form the desired
					 *	projection tuple and return the slot containing it.
					 * ----------------
					 */
					ProjectionInfo *projInfo;
					TupleTableSlot *result;
					bool		isDone;

					MJ_printf("ExecMergeJoin: **** returning tuple ****\n");

					projInfo = mergestate->jstate.cs_ProjInfo;

					result = ExecProject(projInfo, &isDone);
					mergestate->jstate.cs_TupFromTlist = !isDone;
					return result;
				}
				break;

				/*
				 * EXEC_MJ_NEXTINNER means advance the inner scan to the
				 * next tuple. If the tuple is not nil, we then proceed to
				 * test it against the join qualification.
				 */
			case EXEC_MJ_NEXTINNER:
				MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTINNER\n");

				/* ----------------
				 *	now we get the next inner tuple, if any
				 * ----------------
				 */
				innerTupleSlot = ExecProcNode(innerPlan, (Plan *) node);
				MJ_DEBUG_PROC_NODE(innerTupleSlot);
				econtext->ecxt_innertuple = innerTupleSlot;

				if (TupIsNull(innerTupleSlot))
					mergestate->mj_JoinState = EXEC_MJ_NEXTOUTER;
				else
					mergestate->mj_JoinState = EXEC_MJ_JOINTEST;
				break;

				/*-------------------------------------------
				 * EXEC_MJ_NEXTOUTER means
				 *
				 *				outer inner
				 * outer tuple -  5		5  - marked tuple
				 *				  5		5
				 *				  6		6  - inner tuple
				 *				  7		7
				 *
				 * we know we just bumped into the
				 * first inner tuple > current outer tuple
				 * so get a new outer tuple and then
				 * proceed to test it against the marked tuple
				 * (EXEC_MJ_TESTOUTER)
				 *------------------------------------------------
				 */
			case EXEC_MJ_NEXTOUTER:
				MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTOUTER\n");

				outerTupleSlot = ExecProcNode(outerPlan, (Plan *) node);
				MJ_DEBUG_PROC_NODE(outerTupleSlot);
				econtext->ecxt_outertuple = outerTupleSlot;

				/* ----------------
				 *	if the outer tuple is null then we know
				 *	we are done with the join
				 * ----------------
				 */
				if (TupIsNull(outerTupleSlot))
				{
					MJ_printf("ExecMergeJoin: **** outer tuple is nil ****\n");
					return NULL;
				}

				mergestate->mj_JoinState = EXEC_MJ_TESTOUTER;
				break;

				/*--------------------------------------------------------
				 * EXEC_MJ_TESTOUTER If the new outer tuple and the marked
				 * tuple satisfy the merge clause then we know we have
				 * duplicates in the outer scan so we have to restore the
				 * inner scan to the marked tuple and proceed to join the
				 * new outer tuples with the inner tuples (EXEC_MJ_JOINTEST)
				 *
				 * This is the case when
				 *						  outer inner
				 *							4	  5  - marked tuple
				 *			 outer tuple -	5	  5
				 *		 new outer tuple -	5	  5
				 *							6	  8  - inner tuple
				 *							7	 12
				 *
				 *				new outer tuple = marked tuple
				 *
				 *		If the outer tuple fails the test, then we know we have
				 *		to proceed to skip outer tuples until outer >= inner
				 *		(EXEC_MJ_SKIPOUTER).
				 *
				 *		This is the case when
				 *
				 *						  outer inner
				 *							5	  5  - marked tuple
				 *			 outer tuple -	5	  5
				 *		 new outer tuple -	6	  8  - inner tuple
				 *							7	 12
				 *
				 *
				 *		 new outer tuple > marked tuple
				 *
				 *---------------------------------------------------------
				 */
			case EXEC_MJ_TESTOUTER:
				MJ_printf("ExecMergeJoin: EXEC_MJ_TESTOUTER\n");

				/* ----------------
				 *	here we compare the outer tuple with the marked inner tuple
				 *	by using the marked tuple in place of the inner tuple.
				 * ----------------
				 */
				innerTupleSlot = econtext->ecxt_innertuple;
				econtext->ecxt_innertuple = mergestate->mj_MarkedTupleSlot;

				qualResult = ExecQual((List *) mergeclauses, econtext);
				MJ_DEBUG_QUAL(mergeclauses, qualResult);

				if (qualResult)
				{

					/*
					 * the merge clause matched so now we juggle the slots
					 * back the way they were and proceed to JOINTEST.
					 *
					 * I can't understand why we have to go to JOINTEST and
					 * compare outer tuple with the same inner one again
					 * -> go to JOINTUPLES...	 - vadim 02/27/98
					 */

					ExecRestrPos(innerPlan);
#if 0
					mergestate->mj_JoinState = EXEC_MJ_JOINTEST;
#endif
					mergestate->mj_JoinState = EXEC_MJ_JOINTUPLES;

				}
				else
				{
					econtext->ecxt_innertuple = innerTupleSlot;
					/* ----------------
					 *	if the inner tuple was nil and the new outer
					 *	tuple didn't match the marked outer tuple then
					 *	we may have the case:
					 *
					 *			 outer inner
					 *			   4	 4	- marked tuple
					 * new outer - 5	 4
					 *			   6	nil - inner tuple
					 *			   7
					 *
					 *	which means that all subsequent outer tuples will be
					 *	larger than our inner tuples.
					 * ----------------
					 */
					if (TupIsNull(innerTupleSlot))
					{
#ifdef ENABLE_OUTER_JOINS
						if (isLeftJoin)
						{
							/* continue on to null fill outer tuples */
							mergestate->mj_JoinState = EXEC_MJ_FILLOUTER;
							break;
						}
#endif
						MJ_printf("ExecMergeJoin: **** weird case 1 ****\n");
						return NULL;
					}

					/* continue on to skip outer tuples */
					mergestate->mj_JoinState = EXEC_MJ_SKIPOUTER;
				}
				break;

				/*----------------------------------------------------------
				 * EXEC_MJ_SKIPOUTER means skip over tuples in the outer plan
				 * until we find an outer tuple > current inner tuple.
				 *
				 * For example:
				 *
				 *				outer inner
				 *				  5		5
				 *				  5		5
				 * outer tuple -  6		8  - inner tuple
				 *				  7    12
				 *				  8    14
				 *
				 * we have to advance the outer scan
				 * until we find the outer 8.
				 *----------------------------------------------------------
				 */
			case EXEC_MJ_SKIPOUTER:
				MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPOUTER\n");
				/* ----------------
				 *	before we advance, make sure the current tuples
				 *	do not satisfy the mergeclauses.  If they do, then
				 *	we update the marked tuple and go join them.
				 * ----------------
				 */
				qualResult = ExecQual((List *) mergeclauses, econtext);
				MJ_DEBUG_QUAL(mergeclauses, qualResult);

				if (qualResult)
				{
					ExecMarkPos(innerPlan);

					MarkInnerTuple(econtext->ecxt_innertuple, mergestate);

					mergestate->mj_JoinState = EXEC_MJ_JOINTUPLES;
					break;
				}

				/* ----------------
				 *	ok, now test the skip qualification
				 * ----------------
				 */
				compareResult = MergeCompare(mergeclauses,
											 outerSkipQual,
											 econtext);

				MJ_DEBUG_MERGE_COMPARE(outerSkipQual, compareResult);

				/* ----------------
				 *	compareResult is true as long as we should
				 *	continue skipping tuples.
				 * ----------------
				 */
				if (compareResult)
				{
#ifdef ENABLE_OUTER_JOINS
					/* ----------------
					 *	if this is a left or full outer join, then fill
					 * ----------------
					 */
					if (isLeftJoin)
					{
						mergestate->mj_JoinState = EXEC_MJ_FILLOUTER;
						break;
					}
#endif

					outerTupleSlot = ExecProcNode(outerPlan, (Plan *) node);
					MJ_DEBUG_PROC_NODE(outerTupleSlot);
					econtext->ecxt_outertuple = outerTupleSlot;

					/* ----------------
					 *	if the outer tuple is null then we know
					 *	we are done with the join
					 * ----------------
					 */
					if (TupIsNull(outerTupleSlot))
					{
						MJ_printf("ExecMergeJoin: **** outerTuple is nil ****\n");
						return NULL;
					}
					/* ----------------
					 *	otherwise test the new tuple against the skip qual.
					 *	(we remain in the EXEC_MJ_SKIPOUTER state)
					 * ----------------
					 */
					break;
				}

				/* ----------------
				 *	now check the inner skip qual to see if we
				 *	should now skip inner tuples... if we fail the
				 *	inner skip qual, then we know we have a new pair
				 *	of matching tuples.
				 * ----------------
				 */
				compareResult = MergeCompare(mergeclauses,
											 innerSkipQual,
											 econtext);

				MJ_DEBUG_MERGE_COMPARE(innerSkipQual, compareResult);

				if (compareResult)
					mergestate->mj_JoinState = EXEC_MJ_SKIPINNER;
				else
					mergestate->mj_JoinState = EXEC_MJ_JOINMARK;
				break;

				/*-----------------------------------------------------------
				 * EXEC_MJ_SKIPINNER means skip over tuples in the inner plan
				 * until we find an inner tuple > current outer tuple.
				 *