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, 50 insertions, 182 deletions

diff --git a/src/backend/executor/nodeUnique.c b/src/backend/executor/nodeUnique.c
index 6078e0f68a9..f9f1fe81ab3 100644
--- a/src/backend/executor/nodeUnique.c
+++ b/src/backend/executor/nodeUnique.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeUnique.c,v 1.26 2000/01/26 05:56:24 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeUnique.c,v 1.27 2000/01/27 18:11:27 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,79 +29,14 @@
 #include "access/heapam.h"
 #include "access/printtup.h"
 #include "executor/executor.h"
+#include "executor/nodeGroup.h"
 #include "executor/nodeUnique.h"
 
 /* ----------------------------------------------------------------
- *		ExecIdenticalTuples
- *
- *		This is a hack function used by ExecUnique to see if
- *		two tuples are identical.  This should be provided
- *		by the heap tuple code but isn't.  The real problem
- *		is that we assume we can byte compare tuples to determine
- *		if they are "equal".  In fact, if we have user defined
- *		types there may be problems because it's possible that
- *		an ADT may have multiple representations with the
- *		same ADT value. -cim
- * ----------------------------------------------------------------
- */
-static bool						/* true if tuples are identical, false
-								 * otherwise */
-ExecIdenticalTuples(TupleTableSlot *t1, TupleTableSlot *t2)
-{
-	HeapTuple	h1;
-	HeapTuple	h2;
-	char	   *d1;
-	char	   *d2;
-	int			len;
-
-	h1 = t1->val;
-	h2 = t2->val;
-
-	/* ----------------
-	 *	if tuples aren't the same length then they are
-	 *	obviously different (one may have null attributes).
-	 * ----------------
-	 */
-	if (h1->t_len != h2->t_len)
-		return false;
-
-	/* ----------------
-	 *	if the tuples have different header offsets then
-	 *	they are different.  This will prevent us from returning
-	 *	true when comparing tuples of one attribute where one of
-	 *	two we're looking at is null (t_len - t_hoff == 0).
-	 *	THE t_len FIELDS CAN BE THE SAME IN THIS CASE!!
-	 * ----------------
-	 */
-	if (h1->t_data->t_hoff != h2->t_data->t_hoff)
-		return false;
-
-	/* ----------------
-	 *	ok, now get the pointers to the data and the
-	 *	size of the attribute portion of the tuple.
-	 * ----------------
-	 */
-	d1 = (char *) GETSTRUCT(h1);
-	d2 = (char *) GETSTRUCT(h2);
-	len = (int) h1->t_len - (int) h1->t_data->t_hoff;
-
-	/* ----------------
-	 *	byte compare the data areas and return the result.
-	 * ----------------
-	 */
-	if (memcmp(d1, d2, len) != 0)
-		return false;
-
-	return true;
-}
-
-/* ----------------------------------------------------------------
  *		ExecUnique
  *
  *		This is a very simple node which filters out duplicate
  *		tuples from a stream of sorted tuples from a subplan.
- *
- *		XXX see comments below regarding freeing tuples.
  * ----------------------------------------------------------------
  */
 TupleTableSlot *				/* return: a tuple or NULL */
@@ -111,11 +46,7 @@ ExecUnique(Unique *node)
 	TupleTableSlot *resultTupleSlot;
 	TupleTableSlot *slot;
 	Plan	   *outerPlan;
-	char	   *uniqueAttr;
-	AttrNumber	uniqueAttrNum;
 	TupleDesc	tupDesc;
-	Oid			typoutput,
-				typelem;
 
 	/* ----------------
 	 *	get information from the node
@@ -123,22 +54,8 @@ ExecUnique(Unique *node)
 	 */
 	uniquestate = node->uniquestate;
 	outerPlan = outerPlan((Plan *) node);
-	resultTupleSlot = uniquestate->cs_ResultTupleSlot;
-	uniqueAttr = node->uniqueAttr;
-	uniqueAttrNum = node->uniqueAttrNum;
-
-	if (uniqueAttr)
-	{
-		tupDesc = ExecGetResultType(uniquestate);
-		getTypeOutAndElem((Oid) tupDesc->attrs[uniqueAttrNum - 1]->atttypid,
-						  &typoutput, &typelem);
-	}
-	else
-	{							/* keep compiler quiet */
-		tupDesc = NULL;
-		typoutput = InvalidOid;
-		typelem = InvalidOid;
-	}
+	resultTupleSlot = uniquestate->cstate.cs_ResultTupleSlot;
+	tupDesc = ExecGetResultType(& uniquestate->cstate);
 
 	/* ----------------
 	 *	now loop, returning only non-duplicate tuples.
@@ -157,83 +74,38 @@ ExecUnique(Unique *node)
 			return NULL;
 
 		/* ----------------
-		 *	 we use the result tuple slot to hold our saved tuples.
-		 *	 if we haven't a saved tuple to compare our new tuple with,
-		 *	 then we exit the loop. This new tuple as the saved tuple
-		 *	 the next time we get here.
+		 *	 Always return the first tuple from the subplan.
 		 * ----------------
 		 */
-		if (TupIsNull(resultTupleSlot))
+		if (uniquestate->priorTuple == NULL)
 			break;
 
 		/* ----------------
-		 *	 now test if the new tuple and the previous
+		 *	 Else test if the new tuple and the previously returned
 		 *	 tuple match.  If so then we loop back and fetch
 		 *	 another new tuple from the subplan.
 		 * ----------------
 		 */
-
-		if (uniqueAttr)
-		{
-
-			/*
-			 * to check equality, we check to see if the typoutput of the
-			 * attributes are equal
-			 */
-			bool		isNull1,
-						isNull2;
-			Datum		attr1,
-						attr2;
-			char	   *val1,
-					   *val2;
-
-			attr1 = heap_getattr(slot->val,
-								 uniqueAttrNum, tupDesc, &isNull1);
-			attr2 = heap_getattr(resultTupleSlot->val,
-								 uniqueAttrNum, tupDesc, &isNull2);
-
-			if (isNull1 == isNull2)
-			{
-				if (isNull1)	/* both are null, they are equal */
-					continue;
-				val1 = fmgr(typoutput, attr1, typelem,
-							tupDesc->attrs[uniqueAttrNum - 1]->atttypmod);
-				val2 = fmgr(typoutput, attr2, typelem,
-							tupDesc->attrs[uniqueAttrNum - 1]->atttypmod);
-
-				/*
-				 * now, val1 and val2 are ascii representations so we can
-				 * use strcmp for comparison
-				 */
-				if (strcmp(val1, val2) == 0)	/* they are equal */
-				{
-					pfree(val1);
-					pfree(val2);
-					continue;
-				}
-				pfree(val1);
-				pfree(val2);
-				break;
-			}
-			else
-/* one is null and the other isn't, they aren't equal */
-				break;
-
-		}
-		else
-		{
-			if (!ExecIdenticalTuples(slot, resultTupleSlot))
-				break;
-		}
-
+		if (! execTuplesMatch(slot->val, uniquestate->priorTuple,
+							  tupDesc,
+							  node->numCols, node->uniqColIdx,
+							  uniquestate->eqfunctions))
+			break;
 	}
 
 	/* ----------------
-	 *	we have a new tuple different from the previous saved tuple
-	 *	so we save it in the saved tuple slot.	We copy the tuple
-	 *	so we don't increment the buffer ref count.
+	 *	We have a new tuple different from the previous saved tuple (if any).
+	 *	Save it and return it.  Note that we make two copies of the tuple:
+	 *	one to keep for our own future comparisons, and one to return to the
+	 *	caller.  We need to copy the tuple returned by the subplan to avoid
+	 *	holding buffer refcounts, and we need our own copy because the caller
+	 *	may alter the resultTupleSlot (eg via ExecRemoveJunk).
 	 * ----------------
 	 */
+	if (uniquestate->priorTuple != NULL)
+		heap_freetuple(uniquestate->priorTuple);
+	uniquestate->priorTuple = heap_copytuple(slot->val);
+
 	ExecStoreTuple(heap_copytuple(slot->val),
 				   resultTupleSlot,
 				   InvalidBuffer,
@@ -254,7 +126,6 @@ ExecInitUnique(Unique *node, EState *estate, Plan *parent)
 {
 	UniqueState *uniquestate;
 	Plan	   *outerPlan;
-	char	   *uniqueAttr;
 
 	/* ----------------
 	 *	assign execution state to node
@@ -268,10 +139,10 @@ ExecInitUnique(Unique *node, EState *estate, Plan *parent)
 	 */
 	uniquestate = makeNode(UniqueState);
 	node->uniquestate = uniquestate;
-	uniqueAttr = node->uniqueAttr;
+	uniquestate->priorTuple = NULL;
 
 	/* ----------------
-	 *	Miscellanious initialization
+	 *	Miscellaneous initialization
 	 *
 	 *		 +	assign node's base_id
 	 *		 +	assign debugging hooks and
@@ -280,14 +151,14 @@ ExecInitUnique(Unique *node, EState *estate, Plan *parent)
 	 *	they never call ExecQual or ExecTargetList.
 	 * ----------------
 	 */
-	ExecAssignNodeBaseInfo(estate, uniquestate, parent);
+	ExecAssignNodeBaseInfo(estate, & uniquestate->cstate, parent);
 
 #define UNIQUE_NSLOTS 1
 	/* ------------
 	 * Tuple table initialization
 	 * ------------
 	 */
-	ExecInitResultTupleSlot(estate, uniquestate);
+	ExecInitResultTupleSlot(estate, & uniquestate->cstate);
 
 	/* ----------------
 	 *	then initialize outer plan
@@ -301,31 +172,17 @@ ExecInitUnique(Unique *node, EState *estate, Plan *parent)
 	 *	projection info for this node appropriately
 	 * ----------------
 	 */
-	ExecAssignResultTypeFromOuterPlan((Plan *) node, uniquestate);
-	uniquestate->cs_ProjInfo = NULL;
-
-	if (uniqueAttr)
-	{
-		TupleDesc	tupDesc;
-		int			i = 0;
-
-		tupDesc = ExecGetResultType(uniquestate);
-
-		/*
-		 * the parser should have ensured that uniqueAttr is a legal
-		 * attribute name
-		 */
-		while (strcmp(NameStr(tupDesc->attrs[i]->attname), uniqueAttr) != 0)
-			i++;
-		node->uniqueAttrNum = i + 1;	/* attribute numbers start from 1 */
-	}
-	else
-		node->uniqueAttrNum = InvalidAttrNumber;
+	ExecAssignResultTypeFromOuterPlan((Plan *) node, & uniquestate->cstate);
+	uniquestate->cstate.cs_ProjInfo = NULL;
 
-	/* ----------------
-	 *	all done.
-	 * ----------------
+	/*
+	 * Precompute fmgr lookup data for inner loop
 	 */
+	uniquestate->eqfunctions =
+		execTuplesMatchPrepare(ExecGetResultType(& uniquestate->cstate),
+							   node->numCols,
+							   node->uniqColIdx);
+
 	return TRUE;
 }
 
@@ -347,11 +204,17 @@ ExecCountSlotsUnique(Unique *node)
 void
 ExecEndUnique(Unique *node)
 {
-	UniqueState *uniquestate;
+	UniqueState *uniquestate = node->uniquestate;
 
-	uniquestate = node->uniquestate;
 	ExecEndNode(outerPlan((Plan *) node), (Plan *) node);
-	ExecClearTuple(uniquestate->cs_ResultTupleSlot);
+
+	/* clean up tuple table */
+	ExecClearTuple(uniquestate->cstate.cs_ResultTupleSlot);
+	if (uniquestate->priorTuple != NULL)
+	{
+		heap_freetuple(uniquestate->priorTuple);
+		uniquestate->priorTuple = NULL;
+	}
 }
 
 
@@ -360,7 +223,12 @@ ExecReScanUnique(Unique *node, ExprContext *exprCtxt, Plan *parent)
 {
 	UniqueState *uniquestate = node->uniquestate;
 
-	ExecClearTuple(uniquestate->cs_ResultTupleSlot);
+	ExecClearTuple(uniquestate->cstate.cs_ResultTupleSlot);
+	if (uniquestate->priorTuple != NULL)
+	{
+		heap_freetuple(uniquestate->priorTuple);
+		uniquestate->priorTuple = NULL;
+	}
 
 	/*
 	 * if chgParam of subnode is not null then plan will be re-scanned by