Redesign DISTINCT ON as discussed in pgsql-sql 1/25/00: syntax is now

SELECT DISTINCT ON (expr [, expr ...]) targetlist ...
and there is a check to make sure that the user didn't specify an ORDER BY
that's incompatible with the DISTINCT operation.
Reimplement nodeUnique and nodeGroup to use the proper datatype-specific
equality function for each column being compared --- they used to do
bitwise comparisons or convert the data to text strings and strcmp().
(To add insult to injury, they'd look up the conversion functions once
for each tuple...)  Parse/plan representation of DISTINCT is now a list
of SortClause nodes.
initdb forced by querytree change...

1 files changed, 129 insertions, 81 deletions

diff --git a/src/backend/executor/nodeGroup.c b/src/backend/executor/nodeGroup.c
index 017929424bc..cad023776d8 100644
--- a/src/backend/executor/nodeGroup.c
+++ b/src/backend/executor/nodeGroup.c
@@ -9,12 +9,13 @@
  *
  * DESCRIPTION
  *	  The Group node is designed for handling queries with a GROUP BY clause.
- *	  It's outer plan must be a sort node. It assumes that the tuples it gets
- *	  back from the outer plan is sorted in the order specified by the group
- *	  columns. (ie. tuples from the same group are consecutive)
+ *	  Its outer plan must deliver tuples that are sorted in the order
+ *	  specified by the grouping columns (ie. tuples from the same group are
+ *	  consecutive).  That way, we just have to compare adjacent tuples to
+ *	  locate group boundaries.
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeGroup.c,v 1.32 2000/01/26 05:56:22 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeGroup.c,v 1.33 2000/01/27 18:11:27 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -23,13 +24,14 @@
 
 #include "access/heapam.h"
 #include "access/printtup.h"
+#include "catalog/pg_operator.h"
 #include "executor/executor.h"
 #include "executor/nodeGroup.h"
+#include "parser/parse_oper.h"
+#include "parser/parse_type.h"
 
 static TupleTableSlot *ExecGroupEveryTuple(Group *node);
 static TupleTableSlot *ExecGroupOneTuple(Group *node);
-static bool sameGroup(HeapTuple oldslot, HeapTuple newslot,
-		  int numCols, AttrNumber *grpColIdx, TupleDesc tupdesc);
 
 /* ---------------------------------------
  *	 ExecGroup -
@@ -38,11 +40,11 @@ static bool sameGroup(HeapTuple oldslot, HeapTuple newslot,
  *		tuplePerGroup is TRUE, every tuple from the same group will be
  *		returned, followed by a NULL at the end of each group. This is
  *		useful for Agg node which needs to aggregate over tuples of the same
- *		group. (eg. SELECT salary, count{*} FROM emp GROUP BY salary)
+ *		group. (eg. SELECT salary, count(*) FROM emp GROUP BY salary)
  *
  *		If tuplePerGroup is FALSE, only one tuple per group is returned. The
  *		tuple returned contains only the group columns. NULL is returned only
- *		at the end when no more groups is present. This is useful when
+ *		at the end when no more groups are present. This is useful when
  *		the query does not involve aggregates. (eg. SELECT salary FROM emp
  *		GROUP BY salary)
  * ------------------------------------------
@@ -66,6 +68,7 @@ ExecGroupEveryTuple(Group *node)
 	GroupState *grpstate;
 	EState	   *estate;
 	ExprContext *econtext;
+	TupleDesc	tupdesc;
 
 	HeapTuple	outerTuple = NULL;
 	HeapTuple	firsttuple;
@@ -87,6 +90,8 @@ ExecGroupEveryTuple(Group *node)
 
 	econtext = grpstate->csstate.cstate.cs_ExprContext;
 
+	tupdesc = ExecGetScanType(&grpstate->csstate);
+
 	/* if we haven't returned first tuple of new group yet ... */
 	if (grpstate->grp_useFirstTuple)
 	{
@@ -110,20 +115,25 @@ ExecGroupEveryTuple(Group *node)
 		outerTuple = outerslot->val;
 
 		firsttuple = grpstate->grp_firstTuple;
-		/* this should occur on the first call only */
 		if (firsttuple == NULL)
+		{
+			/* this should occur on the first call only */
 			grpstate->grp_firstTuple = heap_copytuple(outerTuple);
+		}
 		else
 		{
-
 			/*
 			 * Compare with first tuple and see if this tuple is of the
 			 * same group.
 			 */
-			if (!sameGroup(firsttuple, outerTuple,
-						   node->numCols, node->grpColIdx,
-						   ExecGetScanType(&grpstate->csstate)))
+			if (! execTuplesMatch(firsttuple, outerTuple,
+								  tupdesc,
+								  node->numCols, node->grpColIdx,
+								  grpstate->eqfunctions))
 			{
+				/*
+				 * No; save the tuple to return it next time, and return NULL
+				 */
 				grpstate->grp_useFirstTuple = TRUE;
 				heap_freetuple(firsttuple);
 				grpstate->grp_firstTuple = heap_copytuple(outerTuple);
@@ -164,6 +174,7 @@ ExecGroupOneTuple(Group *node)
 	GroupState *grpstate;
 	EState	   *estate;
 	ExprContext *econtext;
+	TupleDesc	tupdesc;
 
 	HeapTuple	outerTuple = NULL;
 	HeapTuple	firsttuple;
@@ -185,10 +196,12 @@ ExecGroupOneTuple(Group *node)
 
 	econtext = node->grpstate->csstate.cstate.cs_ExprContext;
 
+	tupdesc = ExecGetScanType(&grpstate->csstate);
+
 	firsttuple = grpstate->grp_firstTuple;
-	/* this should occur on the first call only */
 	if (firsttuple == NULL)
 	{
+		/* this should occur on the first call only */
 		outerslot = ExecProcNode(outerPlan(node), (Plan *) node);
 		if (TupIsNull(outerslot))
 		{
@@ -213,14 +226,14 @@ ExecGroupOneTuple(Group *node)
 		}
 		outerTuple = outerslot->val;
 
-		/* ----------------
-		 *	Compare with first tuple and see if this tuple is of
-		 *	the same group.
-		 * ----------------
+		/*
+		 * Compare with first tuple and see if this tuple is of the
+		 * same group.
 		 */
-		if ((!sameGroup(firsttuple, outerTuple,
-						node->numCols, node->grpColIdx,
-						ExecGetScanType(&grpstate->csstate))))
+		if (! execTuplesMatch(firsttuple, outerTuple,
+							  tupdesc,
+							  node->numCols, node->grpColIdx,
+							  grpstate->eqfunctions))
 			break;
 	}
 
@@ -311,6 +324,14 @@ ExecInitGroup(Group *node, EState *estate, Plan *parent)
 	ExecAssignResultTypeFromTL((Plan *) node, &grpstate->csstate.cstate);
 	ExecAssignProjectionInfo((Plan *) node, &grpstate->csstate.cstate);
 
+	/*
+	 * Precompute fmgr lookup data for inner loop
+	 */
+	grpstate->eqfunctions =
+		execTuplesMatchPrepare(ExecGetScanType(&grpstate->csstate),
+							   node->numCols,
+							   node->grpColIdx);
+
 	return TRUE;
 }
 
@@ -347,94 +368,121 @@ ExecEndGroup(Group *node)
 	}
 }
 
+void
+ExecReScanGroup(Group *node, ExprContext *exprCtxt, Plan *parent)
+{
+	GroupState *grpstate = node->grpstate;
+
+	grpstate->grp_useFirstTuple = FALSE;
+	grpstate->grp_done = FALSE;
+	if (grpstate->grp_firstTuple != NULL)
+	{
+		heap_freetuple(grpstate->grp_firstTuple);
+		grpstate->grp_firstTuple = NULL;
+	}
+
+	if (((Plan *) node)->lefttree &&
+		((Plan *) node)->lefttree->chgParam == NULL)
+		ExecReScan(((Plan *) node)->lefttree, exprCtxt, (Plan *) node);
+}
+
 /*****************************************************************************
- *
+ *		Code shared with nodeUnique.c
  *****************************************************************************/
 
 /*
- * code swiped from nodeUnique.c
+ * execTuplesMatch
+ *		Return true if two tuples match in all the indicated fields.
+ *		This is used to detect group boundaries in nodeGroup, and to
+ *		decide whether two tuples are distinct or not in nodeUnique.
+ *
+ * tuple1, tuple2: the tuples to compare
+ * tupdesc: tuple descriptor applying to both tuples
+ * numCols: the number of attributes to be examined
+ * matchColIdx: array of attribute column numbers
+ * eqFunctions: array of fmgr lookup info for the equality functions to use
  */
-static bool
-sameGroup(HeapTuple oldtuple,
-		  HeapTuple newtuple,
-		  int numCols,
-		  AttrNumber *grpColIdx,
-		  TupleDesc tupdesc)
+bool
+execTuplesMatch(HeapTuple tuple1,
+				HeapTuple tuple2,
+				TupleDesc tupdesc,
+				int numCols,
+				AttrNumber *matchColIdx,
+				FmgrInfo *eqfunctions)
 {
-	bool		isNull1,
-				isNull2;
-	Datum		attr1,
-				attr2;
-	char	   *val1,
-			   *val2;
 	int			i;
-	AttrNumber	att;
-	Oid			typoutput,
-				typelem;
 
-	for (i = 0; i < numCols; i++)
+	/*
+	 * We cannot report a match without checking all the fields, but we
+	 * can report a non-match as soon as we find unequal fields.  So,
+	 * start comparing at the last field (least significant sort key).
+	 * That's the most likely to be different...
+	 */
+	for (i = numCols; --i >= 0; )
 	{
-		att = grpColIdx[i];
-		getTypeOutAndElem((Oid) tupdesc->attrs[att - 1]->atttypid,
-						  &typoutput, &typelem);
-
-		attr1 = heap_getattr(oldtuple,
+		AttrNumber	att = matchColIdx[i];
+		Datum		attr1,
+					attr2;
+		bool		isNull1,
+					isNull2;
+		Datum		equal;
+
+		attr1 = heap_getattr(tuple1,
 							 att,
 							 tupdesc,
 							 &isNull1);
 
-		attr2 = heap_getattr(newtuple,
+		attr2 = heap_getattr(tuple2,
 							 att,
 							 tupdesc,
 							 &isNull2);
 
-		if (isNull1 == isNull2)
-		{
-			if (isNull1)		/* both are null, they are equal */
-				continue;
+		if (isNull1 != isNull2)
+			return FALSE;		/* one null and one not; they aren't equal */
 
-			val1 = fmgr(typoutput, attr1, typelem,
-						tupdesc->attrs[att - 1]->atttypmod);
-			val2 = fmgr(typoutput, attr2, typelem,
-						tupdesc->attrs[att - 1]->atttypmod);
+		if (isNull1)
+			continue;			/* both are null, treat as equal */
 
-			/*
-			 * now, val1 and val2 are ascii representations so we can use
-			 * strcmp for comparison
-			 */
-			if (strcmp(val1, val2) != 0)
-			{
-				pfree(val1);
-				pfree(val2);
-				return FALSE;
-			}
-			pfree(val1);
-			pfree(val2);
-		}
-		else
-		{
-			/* one is null and the other isn't, they aren't equal */
+		/* Apply the type-specific equality function */
+
+		equal = (Datum) (*fmgr_faddr(& eqfunctions[i])) (attr1, attr2);
+
+		if (DatumGetInt32(equal) == 0)
 			return FALSE;
-		}
 	}
 
 	return TRUE;
 }
 
-void
-ExecReScanGroup(Group *node, ExprContext *exprCtxt, Plan *parent)
+/*
+ * execTuplesMatchPrepare
+ *		Look up the equality functions needed for execTuplesMatch.
+ *		The result is a palloc'd array.
+ */
+FmgrInfo *
+execTuplesMatchPrepare(TupleDesc tupdesc,
+					   int numCols,
+					   AttrNumber *matchColIdx)
 {
-	GroupState *grpstate = node->grpstate;
+	FmgrInfo   *eqfunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
+	int			i;
 
-	grpstate->grp_useFirstTuple = FALSE;
-	grpstate->grp_done = FALSE;
-	if (grpstate->grp_firstTuple != NULL)
+	for (i = 0; i < numCols; i++)
 	{
-		heap_freetuple(grpstate->grp_firstTuple);
-		grpstate->grp_firstTuple = NULL;
+		AttrNumber	att = matchColIdx[i];
+		Oid			typid = tupdesc->attrs[att - 1]->atttypid;
+		Operator	eq_operator;
+		Form_pg_operator pgopform;
+
+		eq_operator = oper("=", typid, typid, true);
+		if (!HeapTupleIsValid(eq_operator))
+		{
+			elog(ERROR, "Unable to identify an equality operator for type '%s'",
+				 typeidTypeName(typid));
+		}
+		pgopform = (Form_pg_operator) GETSTRUCT(eq_operator);
+		fmgr_info(pgopform->oprcode, & eqfunctions[i]);
 	}
 
-	if (((Plan *) node)->lefttree &&
-		((Plan *) node)->lefttree->chgParam == NULL)
-		ExecReScan(((Plan *) node)->lefttree, exprCtxt, (Plan *) node);
+	return eqfunctions;
 }