nodemergejoin.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

				 * Set the next state machine state.  The right things will
				 * happen whether we return this join tuple or just fall
				 * through to continue the state machine execution.
				 */
				node->mj_JoinState = EXEC_MJ_NEXTINNER;

				/*
				 * Check the extra qual conditions to see if we actually want
				 * to return this join tuple.  If not, can proceed with merge.
				 * We must distinguish the additional joinquals (which must
				 * pass to consider the tuples "matched" for outer-join logic)
				 * from the otherquals (which must pass before we actually
				 * return the tuple).
				 *
				 * We don't bother with a ResetExprContext here, on the
				 * assumption that we just did one while checking the merge
				 * qual.  One per tuple should be sufficient.  We do have to
				 * set up the econtext links to the tuples for ExecQual to
				 * use.
				 */
				outerTupleSlot = node->mj_OuterTupleSlot;
				econtext->ecxt_outertuple = outerTupleSlot;
				innerTupleSlot = node->mj_InnerTupleSlot;
				econtext->ecxt_innertuple = innerTupleSlot;

				if (node->js.jointype == JOIN_IN &&
					node->mj_MatchedOuter)
					qualResult = false;
				else
				{
					qualResult = (joinqual == NIL ||
								  ExecQual(joinqual, econtext, false));
					MJ_DEBUG_QUAL(joinqual, qualResult);
				}

				if (qualResult)
				{
					node->mj_MatchedOuter = true;
					node->mj_MatchedInner = true;

					qualResult = (otherqual == NIL ||
								  ExecQual(otherqual, econtext, false));
					MJ_DEBUG_QUAL(otherqual, qualResult);

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

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

						result = ExecProject(node->js.ps.ps_ProjInfo,
											 &isDone);

						if (isDone != ExprEndResult)
						{
							node->js.ps.ps_TupFromTlist =
								(isDone == ExprMultipleResult);
							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.
				 *
				 * Before advancing, we check to see if we must emit an
				 * outer-join fill tuple for this inner tuple.
				 */
			case EXEC_MJ_NEXTINNER:
				MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTINNER\n");

				if (doFillInner && !node->mj_MatchedInner)
				{
					/*
					 * Generate a fake join tuple with nulls for the outer
					 * tuple, and return it if it passes the non-join quals.
					 */
					TupleTableSlot *result;

					node->mj_MatchedInner = true;		/* do it only once */

					result = MJFillInner(node);
					if (result)
						return result;
				}

				/*
				 * now we get the next inner tuple, if any.  If there's none,
				 * advance to next outer tuple (which may be able to join to
				 * previously marked tuples).
				 */
				innerTupleSlot = ExecProcNode(innerPlan);
				node->mj_InnerTupleSlot = innerTupleSlot;
				MJ_DEBUG_PROC_NODE(innerTupleSlot);
				node->mj_MatchedInner = false;

				if (TupIsNull(innerTupleSlot))
				{
					node->mj_JoinState = EXEC_MJ_NEXTOUTER;
					break;
				}

				/*
				 * Load up the new inner tuple's comparison values.  If we
				 * see that it contains a NULL and hence can't match any
				 * outer tuple, we can skip the comparison and assume the
				 * new tuple is greater than current outer.
				 */
				if (!MJEvalInnerValues(node, innerTupleSlot))
				{
					node->mj_JoinState = EXEC_MJ_NEXTOUTER;
					break;
				}

				/*
				 * Test the new inner tuple to see if it matches outer.
				 *
				 * If they do match, then we join them and move on to the next
				 * inner tuple (EXEC_MJ_JOINTUPLES).
				 *
				 * If they do not match then advance to next outer tuple.
				 */
				compareResult = MJCompare(node);
				MJ_DEBUG_COMPARE(compareResult);

				if (compareResult == 0)
					node->mj_JoinState = EXEC_MJ_JOINTUPLES;
				else
				{
					Assert(compareResult < 0);
					node->mj_JoinState = EXEC_MJ_NEXTOUTER;
				}
				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 (or possibly
				 * the end of the inner stream)
				 * so get a new outer tuple and then
				 * proceed to test it against the marked tuple
				 * (EXEC_MJ_TESTOUTER)
				 *
				 * Before advancing, we check to see if we must emit an
				 * outer-join fill tuple for this outer tuple.
				 *------------------------------------------------
				 */
			case EXEC_MJ_NEXTOUTER:
				MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTOUTER\n");

				if (doFillOuter && !node->mj_MatchedOuter)
				{
					/*
					 * Generate a fake join tuple with nulls for the inner
					 * tuple, and return it if it passes the non-join quals.
					 */
					TupleTableSlot *result;

					node->mj_MatchedOuter = true;		/* do it only once */

					result = MJFillOuter(node);
					if (result)
						return result;
				}

				/*
				 * now we get the next outer tuple, if any
				 */
				outerTupleSlot = ExecProcNode(outerPlan);
				node->mj_OuterTupleSlot = outerTupleSlot;
				MJ_DEBUG_PROC_NODE(outerTupleSlot);
				node->mj_MatchedOuter = false;

				/*
				 * if the outer tuple is null then we are done with the join,
				 * unless we have inner tuples we need to null-fill.
				 */
				if (TupIsNull(outerTupleSlot))
				{
					MJ_printf("ExecMergeJoin: end of outer subplan\n");
					innerTupleSlot = node->mj_InnerTupleSlot;
					if (doFillInner && !TupIsNull(innerTupleSlot))
					{
						/*
						 * Need to emit right-join tuples for remaining inner
						 * tuples.
						 */
						node->mj_JoinState = EXEC_MJ_ENDOUTER;
						break;
					}
					/* Otherwise we're done. */
					return NULL;
				}

				/* Compute join values and check for unmatchability */
				if (MJEvalOuterValues(node))
				{
					/* Go test the new tuple against the marked tuple */
					node->mj_JoinState = EXEC_MJ_TESTOUTER;
				}
				else
				{
					/* Can't match, so fetch next outer tuple */
					node->mj_JoinState = EXEC_MJ_NEXTOUTER;
				}
				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 tuple with the inner tuples.
				 *
				 * 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 are done
				 * with the marked tuples, and we have to look for a
				 * match to the current inner tuple.  So we will
				 * proceed to skip outer tuples until outer >= inner
				 * (EXEC_MJ_SKIP_TEST).
				 *
				 *		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 must compare the outer tuple with the marked inner
				 * tuple.  (We can ignore the result of MJEvalInnerValues,
				 * since the marked inner tuple is certainly matchable.)
				 */
				innerTupleSlot = node->mj_MarkedTupleSlot;
				(void) MJEvalInnerValues(node, innerTupleSlot);

				compareResult = MJCompare(node);
				MJ_DEBUG_COMPARE(compareResult);

				if (compareResult == 0)
				{
					/*
					 * the merge clause matched so now we restore the inner
					 * scan position to the first mark, and go join that tuple
					 * (and any following ones) to the new outer.
					 *
					 * NOTE: we do not need to worry about the MatchedInner
					 * state for the rescanned inner tuples.  We know all of
					 * them will match this new outer tuple and therefore
					 * won't be emitted as fill tuples.  This works *only*
					 * because we require the extra joinquals to be nil when
					 * doing a right or full join --- otherwise some of the
					 * rescanned tuples might fail the extra joinquals.
					 */
					ExecRestrPos(innerPlan);

					/*
					 * ExecRestrPos probably should give us back a new Slot,
					 * but since it doesn't, use the marked slot.  (The
					 * previously returned mj_InnerTupleSlot cannot be assumed
					 * to hold the required tuple.)
					 */
					node->mj_InnerTupleSlot = innerTupleSlot;
					/* we need not do MJEvalInnerValues again */

					node->mj_JoinState = EXEC_MJ_JOINTUPLES;
				}
				else
				{
					/* ----------------
					 *	if the new outer tuple didn't match the marked inner
					 *	tuple then we have a case like:
					 *
					 *			 outer inner
					 *			   4	 4	- marked tuple
					 * new outer - 5	 4
					 *			   6	 5	- inner tuple
					 *			   7
					 *
					 *	which means that all subsequent outer tuples will be
					 *	larger than our marked inner tuples.  So we need not
					 *	revisit any of the marked tuples but can proceed to
					 *	look for a match to the current inner.	If there's
					 *	no more inners, we are done.
					 * ----------------
					 */
					Assert(compareResult > 0);
					innerTupleSlot = node->mj_InnerTupleSlot;
					if (TupIsNull(innerTupleSlot))
					{
						if (doFillOuter)
						{
							/*
							 * Need to emit left-join tuples for remaining
							 * outer tuples.
							 */
							node->mj_JoinState = EXEC_MJ_ENDINNER;
							break;
						}
						/* Otherwise we're done. */
						return NULL;
					}

					/* reload comparison data for current inner */
					if (MJEvalInnerValues(node, innerTupleSlot))
					{
						/* proceed to compare it to the current outer */
						node->mj_JoinState = EXEC_MJ_SKIP_TEST;
					}
					else
					{
						/*
						 * current inner can't possibly match any outer;
						 * better to advance the inner scan than the outer.
						 */
						node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
					}
				}
				break;

				/*----------------------------------------------------------
				 * EXEC_MJ_SKIP means compare tuples and if they do not
				 * match, skip whichever is lesser.
				 *
				 * 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.
				 *
				 * On the other hand:
				 *
				 *				outer inner
				 *				  5		5
				 *				  5		5
				 * outer tuple - 12		8  - inner tuple
				 *				 14    10
				 *				 17    12
				 *
				 * we have to advance the inner scan
				 * until we find the inner 12.
				 *----------------------------------------------------------
				 */
			case EXEC_MJ_SKIP_TEST:
				MJ_printf("ExecMergeJoin: EXEC_MJ_SKIP_TEST\n");

				/*
				 * before we advance, make sure the current tuples do not
				 * satisfy the mergeclauses.  If they do, then we update the
				 * marked tuple position and go join them.
				 */
				compareResult = MJCompare(node);
				MJ_DEBUG_COMPARE(compareResult);

				if (compareResult == 0)
				{
					ExecMarkPos(innerPlan);

					MarkInnerTuple(node->mj_InnerTupleSlot, node);

					node->mj_JoinState = EXEC_MJ_JOINTUPLES;
				}
				else if (compareResult < 0)
					node->mj_JoinState = EXEC_MJ_SKIPOUTER_ADVANCE;
				else
					/* compareResult > 0 */
					node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
				break;

				/*
				 * Before advancing, we check to see if we must emit an
				 * outer-join fill tuple for this outer tuple.
				 */
			case EXEC_MJ_SKIPOUTER_ADVANCE:
				MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPOUTER_ADVANCE\n");

				if (doFillOuter && !node->mj_MatchedOuter)
				{
					/*
					 * Generate a fake join tuple with nulls for the inner
					 * tuple, and return it if it passes the non-join quals.
					 */
					TupleTableSlot *result;

					node->mj_MatchedOuter = true;		/* do it only once */

					result = MJFillOuter(node);
					if (result)