COALESCE() and NULLIF() are now first-class expressions, not macros

that turn into CASE expressions.  They evaluate their arguments at most
once.  Patch by Kris Jurka, review and (very light) editorializing by me.

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.243 2003/02/10 04:44:44 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.244 2003/02/16 02:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -785,7 +785,7 @@ _copyOpExpr(OpExpr *from)
 }
 
 /*
- * _copyDistinctExpr
+ * _copyDistinctExpr (same as OpExpr)
  */
 static DistinctExpr *
 _copyDistinctExpr(DistinctExpr *from)
@@ -919,6 +919,37 @@ _copyCaseWhen(CaseWhen *from)
 	return newnode;
 }
 
+/*
+ * _copyCoalesceExpr
+ */
+static CoalesceExpr *
+_copyCoalesceExpr(CoalesceExpr *from)
+{
+	CoalesceExpr *newnode = makeNode(CoalesceExpr);
+
+	COPY_SCALAR_FIELD(coalescetype);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+/*
+ * _copyNullIfExpr (same as OpExpr)
+ */
+static NullIfExpr *
+_copyNullIfExpr(NullIfExpr *from)
+{
+	NullIfExpr	   *newnode = makeNode(NullIfExpr);
+
+	COPY_SCALAR_FIELD(opno);
+	COPY_SCALAR_FIELD(opfuncid);
+	COPY_SCALAR_FIELD(opresulttype);
+	COPY_SCALAR_FIELD(opretset);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 /*
  * _copyNullTest
  */
@@ -2484,6 +2515,12 @@ copyObject(void *from)
 		case T_CaseWhen:
 			retval = _copyCaseWhen(from);
 			break;
+		case T_CoalesceExpr:
+			retval = _copyCoalesceExpr(from);
+			break;
+		case T_NullIfExpr:
+			retval = _copyNullIfExpr(from);
+			break;
 		case T_NullTest:
 			retval = _copyNullTest(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -18,7 +18,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.186 2003/02/10 04:44:45 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.187 2003/02/16 02:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -378,6 +378,37 @@ _equalCaseWhen(CaseWhen *a, CaseWhen *b)
 	return true;
 }
 
+static bool
+_equalCoalesceExpr(CoalesceExpr *a, CoalesceExpr *b)
+{
+	COMPARE_SCALAR_FIELD(coalescetype);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalNullIfExpr(NullIfExpr *a, NullIfExpr *b)
+{
+	COMPARE_SCALAR_FIELD(opno);
+	/*
+	 * Special-case opfuncid: it is allowable for it to differ if one
+	 * node contains zero and the other doesn't.  This just means that the
+	 * one node isn't as far along in the parse/plan pipeline and hasn't
+	 * had the opfuncid cache filled yet.
+	 */
+	if (a->opfuncid != b->opfuncid &&
+		a->opfuncid != 0 &&
+		b->opfuncid != 0)
+		return false;
+
+	COMPARE_SCALAR_FIELD(opresulttype);
+	COMPARE_SCALAR_FIELD(opretset);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
 static bool
 _equalNullTest(NullTest *a, NullTest *b)
 {
@@ -1613,6 +1644,12 @@ equal(void *a, void *b)
 		case T_CaseWhen:
 			retval = _equalCaseWhen(a, b);
 			break;
+		case T_CoalesceExpr:
+			retval = _equalCoalesceExpr(a, b);
+			break;
+		case T_NullIfExpr:
+			retval = _equalNullIfExpr(a, b);
+			break;
 		case T_NullTest:
 			retval = _equalNullTest(a, b);
 			break;

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/outfuncs.c,v 1.199 2003/02/10 04:44:45 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/outfuncs.c,v 1.200 2003/02/16 02:30:37 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -753,6 +753,27 @@ _outCaseWhen(StringInfo str, CaseWhen *node)
 	WRITE_NODE_FIELD(result);
 }
 
+static void
+_outCoalesceExpr(StringInfo str, CoalesceExpr *node)
+{
+	WRITE_NODE_TYPE("COALESCE");
+
+	WRITE_OID_FIELD(coalescetype);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outNullIfExpr(StringInfo str, NullIfExpr *node)
+{
+	WRITE_NODE_TYPE("NULLIFEXPR");
+
+	WRITE_OID_FIELD(opno);
+	WRITE_OID_FIELD(opfuncid);
+	WRITE_OID_FIELD(opresulttype);
+	WRITE_BOOL_FIELD(opretset);
+	WRITE_NODE_FIELD(args);
+}
+
 static void
 _outNullTest(StringInfo str, NullTest *node)
 {
@@ -1277,6 +1298,10 @@ _outAExpr(StringInfo str, A_Expr *node)
 			appendStringInfo(str, " DISTINCT ");
 			WRITE_NODE_FIELD(name);
 			break;
+		case AEXPR_NULLIF:
+			appendStringInfo(str, " NULLIF ");
+			WRITE_NODE_FIELD(name);
+			break;
 		case AEXPR_OF:
 			appendStringInfo(str, " OF ");
 			WRITE_NODE_FIELD(name);
@@ -1576,6 +1601,12 @@ _outNode(StringInfo str, void *obj)
 			case T_CaseWhen:
 				_outCaseWhen(str, obj);
 				break;
+			case T_CoalesceExpr:
+				_outCoalesceExpr(str, obj);
+				break;
+			case T_NullIfExpr:
+				_outNullIfExpr(str, obj);
+				break;
 			case T_NullTest:
 				_outNullTest(str, obj);
 				break;

src/backend/nodes/readfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.148 2003/02/09 06:56:27 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.149 2003/02/16 02:30:37 tgl Exp $
  *
  * NOTES
  *	  Path and Plan nodes do not have any readfuncs support, because we
@@ -606,6 +606,47 @@ _readCaseWhen(void)
 	READ_DONE();
 }
 
+/*
+ * _readCoalesceExpr
+ */
+static CoalesceExpr *
+_readCoalesceExpr(void)
+{
+	READ_LOCALS(CoalesceExpr);
+
+	READ_OID_FIELD(coalescetype);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readNullIfExpr
+ */
+static NullIfExpr *
+_readNullIfExpr(void)
+{
+	READ_LOCALS(NullIfExpr);
+
+	READ_OID_FIELD(opno);
+	READ_OID_FIELD(opfuncid);
+	/*
+	 * The opfuncid is stored in the textual format primarily for debugging
+	 * and documentation reasons.  We want to always read it as zero to force
+	 * it to be re-looked-up in the pg_operator entry.  This ensures that
+	 * stored rules don't have hidden dependencies on operators' functions.
+	 * (We don't currently support an ALTER OPERATOR command, but might
+	 * someday.)
+	 */
+	local_node->opfuncid = InvalidOid;
+
+	READ_OID_FIELD(opresulttype);
+	READ_BOOL_FIELD(opretset);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
 /*
  * _readNullTest
  */
@@ -895,6 +936,10 @@ parseNodeString(void)
 		return_value = _readCaseExpr();
 	else if (MATCH("WHEN", 4))
 		return_value = _readCaseWhen();
+	else if (MATCH("COALESCE", 8))
+		return_value = _readCoalesceExpr();
+	else if (MATCH("NULLIFEXPR", 10))
+		return_value = _readNullIfExpr();
 	else if (MATCH("NULLTEST", 8))
 		return_value = _readNullTest();
 	else if (MATCH("BOOLEANTEST", 11))