Add IS UNKNOWN, IS NOT UNKNOWN boolean tests, fix the existing boolean

tests to return the correct results per SQL9x when given NULL inputs.
Reimplement these tests as well as IS [NOT] NULL to have their own
expression node types, instead of depending on special functions.
From Joe Conway, with a little help from Tom Lane.

1 files changed, 14 insertions, 18 deletions

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 02c6a4ac8c7..585b21b0f45 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.80 2001/05/18 21:24:19 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.81 2001/06/19 22:39:11 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -286,16 +286,14 @@ transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars)
 	 */
 	result = transformExpr(pstate, result, EXPR_COLUMN_FIRST);
 
+	/*
+	 * We expect the result to yield bool directly, otherwise complain.
+	 * We could try coerce_to_boolean() here, but it seems likely that an
+	 * "=" operator that doesn't return bool is wrong anyway.
+	 */
 	if (exprType(result) != BOOLOID)
-	{
-
-		/*
-		 * This could only happen if someone defines a funny version of
-		 * '='
-		 */
 		elog(ERROR, "JOIN/USING clause must return type bool, not type %s",
 			 typeidTypeName(exprType(result)));
-	}
 
 	return result;
 }	/* transformJoinUsingClause() */
@@ -328,11 +326,10 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j,
 
 	/* This part is just like transformWhereClause() */
 	result = transformExpr(pstate, j->quals, EXPR_COLUMN_FIRST);
-	if (exprType(result) != BOOLOID)
-	{
+
+	if (! coerce_to_boolean(pstate, &result))
 		elog(ERROR, "JOIN/ON clause must return type bool, not type %s",
 			 typeidTypeName(exprType(result)));
-	}
 
 	pstate->p_namespace = save_namespace;
 
@@ -689,11 +686,11 @@ transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels)
 							/* Need COALESCE(l_colvar, r_colvar) */
 							CaseExpr   *c = makeNode(CaseExpr);
 							CaseWhen   *w = makeNode(CaseWhen);
-							A_Expr	   *a = makeNode(A_Expr);
+							NullTest   *n = makeNode(NullTest);
 
-							a->oper = NOTNULL;
-							a->lexpr = l_colvar;
-							w->expr = (Node *) a;
+							n->arg = l_colvar;
+							n->nulltesttype = IS_NOT_NULL;
+							w->expr = (Node *) n;
 							w->result = l_colvar;
 							c->args = makeList1(w);
 							c->defresult = r_colvar;
@@ -777,11 +774,10 @@ transformWhereClause(ParseState *pstate, Node *clause)
 
 	qual = transformExpr(pstate, clause, EXPR_COLUMN_FIRST);
 
-	if (exprType(qual) != BOOLOID)
-	{
+	if (! coerce_to_boolean(pstate, &qual))
 		elog(ERROR, "WHERE clause must return type bool, not type %s",
 			 typeidTypeName(exprType(qual)));
-	}
+
 	return qual;
 }