Make constant-folding produce sane output for COALESCE(NULL,NULL),

tglsfdc · tglsfdc · commit acde8b3cab48 · 2005-04-10T20:57:32.000Z
that is a plain NULL and not a COALESCE with no inputs.  Fixes crash
reported by Michael Williamson.
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.193 2005/04/06 16:34:06 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.194 2005/04/10 20:57:32 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -1788,6 +1788,10 @@ eval_const_expressions_mutator(Node *node,
 			newargs = lappend(newargs, e);
 		}
 
+		/* If all the arguments were constant null, the result is just null */
+		if (newargs == NIL)
+			return (Node *) makeNullConst(coalesceexpr->coalescetype);
+
 		newcoalesce = makeNode(CoalesceExpr);
 		newcoalesce->coalescetype = coalesceexpr->coalescetype;
 		newcoalesce->args = newargs;

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`*`
`9`	`9`	`*`
`10`	`10`	`* IDENTIFICATION`
`11`		`- * $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.193 2005/04/06 16:34:06 tgl Exp $`
	`11`	`+ * $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.194 2005/04/10 20:57:32 tgl Exp $`
`12`	`12`	`*`
`13`	`13`	`* HISTORY`
`14`	`14`	`* AUTHOR DATE MAJOR EVENT`
`@@ -1788,6 +1788,10 @@ eval_const_expressions_mutator(Node *node,`
`1788`	`1788`	`newargs = lappend(newargs, e);`
`1789`	`1789`	`}`
`1790`	`1790`
	`1791`	`+ /* If all the arguments were constant null, the result is just null */`
	`1792`	`+ if (newargs == NIL)`
	`1793`	`+ return (Node *) makeNullConst(coalesceexpr->coalescetype);`
	`1794`	`+`
`1791`	`1795`	`newcoalesce = makeNode(CoalesceExpr);`
`1792`	`1796`	`newcoalesce->coalescetype = coalesceexpr->coalescetype;`
`1793`	`1797`	`newcoalesce->args = newargs;`