optimiser/evaluator: fix case expression evaluation.

zhouziqunzzq · Jan 15, 2016 · b6a0f5b · b6a0f5b
1 parent 70bfab8
commit b6a0f5b
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diff --git a/optimizer/evaluator/evaluator.go b/optimizer/evaluator/evaluator.go
@@ -205,6 +205,8 @@ func (e *Evaluator) caseExpr(v *ast.CaseExpr) bool {
 	}
 	if v.ElseClause != nil {
 		v.SetValue(v.ElseClause.GetValue())
+	} else {
+		v.SetValue(nil)
 	}
 	return true
 }

diff --git a/optimizer/evaluator/evaluator_test.go b/optimizer/evaluator/evaluator_test.go
@@ -333,6 +333,22 @@ func (s *testEvaluatorSuite) TestCaseWhen(c *C) {
 		},
 	}
 	s.runTests(c, cases)
+
+	// When expression value changed, result set back to null.
+	valExpr := ast.NewValueExpr(1)
+	whenClause := &ast.WhenClause{Expr: ast.NewValueExpr(1), Result: ast.NewValueExpr(1)}
+	caseExpr := &ast.CaseExpr{
+		Value:       valExpr,
+		WhenClauses: []*ast.WhenClause{whenClause},
+	}
+	ctx := mock.NewContext()
+	v, err := Eval(ctx, caseExpr)
+	c.Assert(err, IsNil)
+	c.Assert(v, Equals, 1)
+	valExpr.SetValue(4)
+	v, err = Eval(ctx, caseExpr)
+	c.Assert(err, IsNil)
+	c.Assert(v, IsNil)
 }
 
 func (s *testEvaluatorSuite) TestConvert(c *C) {