Change the planner-to-executor API so that the planner tells the executor

which comparison operators to use for plan nodes involving tuple comparison
(Agg, Group, Unique, SetOp).  Formerly the executor looked up the default
equality operator for the datatype, which was really pretty shaky, since it's
possible that the data being fed to the node is sorted according to some
nondefault operator class that could have an incompatible idea of equality.
The planner knows what it has sorted by and therefore can provide the right
equality operator to use.  Also, this change moves a couple of catalog lookups
out of the executor and into the planner, which should help startup time for
pre-planned queries by some small amount.  Modify the planner to remove some
other cavalier assumptions about always being able to use the default
operators.  Also add "nulls first/last" info to the Plan node for a mergejoin
--- neither the executor nor the planner can cope yet, but at least the API is
in place.

1 files changed, 19 insertions, 21 deletions

diff --git a/src/backend/executor/nodeMergejoin.c b/src/backend/executor/nodeMergejoin.c
index 63e9035f546..a5f08c28ef3 100644
--- a/src/backend/executor/nodeMergejoin.c
+++ b/src/backend/executor/nodeMergejoin.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.84 2007/01/05 22:19:28 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.85 2007/01/10 18:06:02 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -156,35 +156,36 @@ typedef struct MergeJoinClauseData
  * the two expressions from the original clause.
  *
  * In addition to the expressions themselves, the planner passes the btree
- * opfamily OID and btree strategy number (BTLessStrategyNumber or
- * BTGreaterStrategyNumber) that identify the intended merge semantics for
- * each merge key.  The mergejoinable operator is an equality operator in
- * this opfamily, and the two inputs are guaranteed to be ordered in either
- * increasing or decreasing (respectively) order according to this opfamily.
- * This allows us to obtain the needed comparison functions from the opfamily.
+ * opfamily OID, btree strategy number (BTLessStrategyNumber or
+ * BTGreaterStrategyNumber), and nulls-first flag that identify the intended
+ * merge semantics for each merge key.  The mergejoinable operator is an
+ * equality operator in this opfamily, and the two inputs are guaranteed to be
+ * ordered in either increasing or decreasing (respectively) order according
+ * to this opfamily.  This allows us to obtain the needed comparison functions
+ * from the opfamily.
  */
 static MergeJoinClause
-MJExamineQuals(List *mergeclauses, List *mergefamilies, List *mergestrategies,
+MJExamineQuals(List *mergeclauses,
+			   Oid *mergefamilies,
+			   int *mergestrategies,
+			   bool *mergenullsfirst,
 			   PlanState *parent)
 {
 	MergeJoinClause clauses;
 	int			nClauses = list_length(mergeclauses);
 	int			iClause;
 	ListCell   *cl;
-	ListCell   *cf;
-	ListCell   *cs;
 
 	clauses = (MergeJoinClause) palloc0(nClauses * sizeof(MergeJoinClauseData));
 
 	iClause = 0;
-	cf = list_head(mergefamilies);
-	cs = list_head(mergestrategies);
 	foreach(cl, mergeclauses)
 	{
 		OpExpr	   *qual = (OpExpr *) lfirst(cl);
 		MergeJoinClause clause = &clauses[iClause];
-		Oid			opfamily;
-		StrategyNumber opstrategy;
+		Oid			opfamily = mergefamilies[iClause];
+		StrategyNumber opstrategy = mergestrategies[iClause];
+		bool		nulls_first = mergenullsfirst[iClause];
 		int			op_strategy;
 		Oid			op_lefttype;
 		Oid			op_righttype;
@@ -192,14 +193,10 @@ MJExamineQuals(List *mergeclauses, List *mergefamilies, List *mergestrategies,
 		RegProcedure cmpproc;
 		AclResult	aclresult;
 
-		opfamily = lfirst_oid(cf);
-		cf = lnext(cf);
-		opstrategy = lfirst_int(cs);
-		cs = lnext(cs);
-
 		/* Later we'll support both ascending and descending sort... */
 		Assert(opstrategy == BTLessStrategyNumber);
 		clause->cmpstrategy = MERGEFUNC_CMP;
+		Assert(!nulls_first);
 
 		if (!IsA(qual, OpExpr))
 			elog(ERROR, "mergejoin clause is not an OpExpr");
@@ -1525,8 +1522,9 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 	 */
 	mergestate->mj_NumClauses = list_length(node->mergeclauses);
 	mergestate->mj_Clauses = MJExamineQuals(node->mergeclauses,
-											node->mergefamilies,
-											node->mergestrategies,
+											node->mergeFamilies,
+											node->mergeStrategies,
+											node->mergeNullsFirst,
 											(PlanState *) mergestate);
 
 	/*