Add Oracle-compatible GREATEST and LEAST functions. Pavel Stehule

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.497 2005/06/24 14:28:06 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.498 2005/06/26 22:05:38 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -360,7 +360,7 @@ static void doNegateFloat(Value *v);
 	FALSE_P FETCH FIRST_P FLOAT_P FOR FORCE FOREIGN FORWARD
 	FREEZE FROM FULL FUNCTION
 
-	GLOBAL GRANT GROUP_P
+	GLOBAL GRANT GREATEST GROUP_P
 
 	HANDLER HAVING HEADER HOLD HOUR_P
 
@@ -373,8 +373,8 @@ static void doNegateFloat(Value *v);
 
 	KEY
 
-	LANCOMPILER LANGUAGE LARGE_P LAST_P LEADING LEFT LEVEL LIKE LIMIT
-	LISTEN LOAD LOCAL LOCALTIME LOCALTIMESTAMP LOCATION
+	LANCOMPILER LANGUAGE LARGE_P  LAST_P LEADING LEAST LEFT LEVEL
+	LIKE LIMIT LISTEN LOAD LOCAL LOCALTIME LOCALTIMESTAMP LOCATION
 	LOCK_P
 
 	MATCH MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
@@ -1154,7 +1154,7 @@ AlterTableStmt:
 					AlterTableStmt *n = makeNode(AlterTableStmt);
 					n->relation = $3;
 					n->cmds = $4;
-					n->relkind = OBJECT_TABLE; 
+					n->relkind = OBJECT_TABLE;
 					$$ = (Node *)n;
 				}
 		|	ALTER INDEX relation_expr alter_rel_cmds
@@ -3821,7 +3821,7 @@ opt_column: COLUMN									{ $$ = COLUMN; }
 
 /*****************************************************************************
  *
- * ALTER THING name OWNER TO newname.  
+ * ALTER THING name OWNER TO newname.
  *
  *****************************************************************************/
 
@@ -6373,7 +6373,7 @@ a_expr:		c_expr									{ $$ = $1; }
 						    (Node *) makeSimpleA_Expr(AEXPR_OP, "<=", $1, $6)),
 						(Node *) makeA_Expr(AEXPR_AND, NIL,
 						    (Node *) makeSimpleA_Expr(AEXPR_OP, ">=", $1, $6),
-						    (Node *) makeSimpleA_Expr(AEXPR_OP, "<=", $1, $4)));					
+						    (Node *) makeSimpleA_Expr(AEXPR_OP, "<=", $1, $4)));
 				}
 			| a_expr NOT BETWEEN SYMMETRIC b_expr AND b_expr		%prec BETWEEN
 				{
@@ -6383,7 +6383,7 @@ a_expr:		c_expr									{ $$ = $1; }
 						    (Node *) makeSimpleA_Expr(AEXPR_OP, ">", $1, $7)),
 						(Node *) makeA_Expr(AEXPR_OR, NIL,
 						    (Node *) makeSimpleA_Expr(AEXPR_OP, "<", $1, $7),
-						    (Node *) makeSimpleA_Expr(AEXPR_OP, ">", $1, $5)));					
+						    (Node *) makeSimpleA_Expr(AEXPR_OP, ">", $1, $5)));
 				}
 			| a_expr IN_P in_expr
 				{
@@ -7065,6 +7065,20 @@ func_expr:	func_name '(' ')'
 					c->args = $3;
 					$$ = (Node *)c;
 				}
+			| GREATEST '(' expr_list ')'
+				{
+					MinMaxExpr *v = makeNode(MinMaxExpr);
+					v->args = $3;
+					v->op = IS_GREATEST;
+					$$ = (Node *)v;
+				}
+			| LEAST '(' expr_list ')'
+				{
+					MinMaxExpr *v = makeNode(MinMaxExpr);
+					v->args = $3;
+					v->op = IS_LEAST;
+					$$ = (Node *)v;
+				}
 		;
 
 /*
@@ -7944,10 +7958,12 @@ col_name_keyword:
 			| EXISTS
 			| EXTRACT
 			| FLOAT_P
+			| GREATEST
 			| INOUT
 			| INT_P
 			| INTEGER
 			| INTERVAL
+			| LEAST
 			| NATIONAL
 			| NCHAR
 			| NONE

src/backend/parser/keywords.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/keywords.c,v 1.158 2005/06/22 21:14:30 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/keywords.c,v 1.159 2005/06/26 22:05:39 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -146,6 +146,7 @@ static const ScanKeyword ScanKeywords[] = {
 	{"function", FUNCTION},
 	{"global", GLOBAL},
 	{"grant", GRANT},
+	{"greatest", GREATEST},
 	{"group", GROUP_P},
 	{"handler", HANDLER},
 	{"having", HAVING},
@@ -184,6 +185,7 @@ static const ScanKeyword ScanKeywords[] = {
 	{"large", LARGE_P},
 	{"last", LAST_P},
 	{"leading", LEADING},
+	{"least", LEAST},
 	{"left", LEFT},
 	{"level", LEVEL},
 	{"like", LIKE},

src/backend/parser/parse_expr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.183 2005/06/04 20:56:13 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.184 2005/06/26 22:05:39 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,7 @@ static Node *transformSubLink(ParseState *pstate, SubLink *sublink);
 static Node *transformArrayExpr(ParseState *pstate, ArrayExpr *a);
 static Node *transformRowExpr(ParseState *pstate, RowExpr *r);
 static Node *transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c);
+static Node *transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m);
 static Node *transformBooleanTest(ParseState *pstate, BooleanTest *b);
 static Node *transformColumnRef(ParseState *pstate, ColumnRef *cref);
 static Node *transformWholeRowRef(ParseState *pstate, char *schemaname,
@@ -209,6 +210,10 @@ transformExpr(ParseState *pstate, Node *expr)
 			result = transformCoalesceExpr(pstate, (CoalesceExpr *) expr);
 			break;
 
+		case T_MinMaxExpr:
+			result = transformMinMaxExpr(pstate, (MinMaxExpr *) expr);
+			break;
+
 		case T_NullTest:
 			{
 				NullTest   *n = (NullTest *) expr;
@@ -1229,6 +1234,44 @@ transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c)
 	return (Node *) newc;
 }
 
+static Node *
+transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m)
+{
+	MinMaxExpr *newm = makeNode(MinMaxExpr);
+	List	   *newargs = NIL;
+	List	   *newcoercedargs = NIL;
+	List	   *typeids = NIL;
+	ListCell   *args;
+
+	newm->op = m->op;
+	foreach(args, m->args)
+	{
+		Node	   *e = (Node *) lfirst(args);
+		Node	   *newe;
+
+		newe = transformExpr(pstate, e);
+		newargs = lappend(newargs, newe);
+		typeids = lappend_oid(typeids, exprType(newe));
+	}
+
+	newm->minmaxtype = select_common_type(typeids, "GREATEST/LEAST");
+
+	/* Convert arguments if necessary */
+	foreach(args, newargs)
+	{
+		Node	   *e = (Node *) lfirst(args);
+		Node	   *newe;
+
+		newe = coerce_to_common_type(pstate, e,
+									 newm->minmaxtype,
+									 "GREATEST/LEAST");
+		newcoercedargs = lappend(newcoercedargs, newe);
+	}
+
+	newm->args = newcoercedargs;
+	return (Node *) newm;
+}
+
 static Node *
 transformBooleanTest(ParseState *pstate, BooleanTest *b)
 {
@@ -1503,6 +1546,9 @@ exprType(Node *expr)
 		case T_CoalesceExpr:
 			type = ((CoalesceExpr *) expr)->coalescetype;
 			break;
+		case T_MinMaxExpr:
+			type = ((MinMaxExpr *) expr)->minmaxtype;
+			break;
 		case T_NullIfExpr:
 			type = exprType((Node *) linitial(((NullIfExpr *) expr)->args));
 			break;
@@ -1637,6 +1683,30 @@ exprTypmod(Node *expr)
 				return typmod;
 			}
 			break;
+		case T_MinMaxExpr:
+			{
+				/*
+				 * If all the alternatives agree on type/typmod, return
+				 * that typmod, else use -1
+				 */
+				MinMaxExpr *mexpr = (MinMaxExpr *) expr;
+				Oid			minmaxtype = mexpr->minmaxtype;
+				int32		typmod;
+				ListCell   *arg;
+
+				typmod = exprTypmod((Node *) linitial(mexpr->args));
+				foreach(arg, mexpr->args)
+				{
+					Node	   *e = (Node *) lfirst(arg);
+
+					if (exprType(e) != minmaxtype)
+						return -1;
+					if (exprTypmod(e) != typmod)
+						return -1;
+				}
+				return typmod;
+			}
+			break;
 		case T_NullIfExpr:
 			{
 				NullIfExpr *nexpr = (NullIfExpr *) expr;

src/backend/parser/parse_target.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_target.c,v 1.136 2005/06/05 00:38:10 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_target.c,v 1.137 2005/06/26 22:05:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1123,6 +1123,18 @@ FigureColnameInternal(Node *node, char **name)
 			/* make coalesce() act like a regular function */
 			*name = "coalesce";
 			return 2;
+		case T_MinMaxExpr:
+			/* make greatest/least act like a regular function */
+			switch (((MinMaxExpr*) node)->op)
+			{
+				case IS_GREATEST:
+					*name = "greatest";
+					return 2;
+				case IS_LEAST:
+					*name = "least";
+					return 2;
+			}
+			break;
 		default:
 			break;
 	}