planner: fix expression rewriter wrong compare logic (#8269)

planner/core/expression_rewriter.go

@@ -170,15 +170,11 @@ type expressionRewriter struct {
 }
 
 // 1. If op are EQ or NE or NullEQ, constructBinaryOpFunctions converts (a0,a1,a2) op (b0,b1,b2) to (a0 op b0) and (a1 op b1) and (a2 op b2)
-// 2. If op are LE or GE, constructBinaryOpFunctions converts (a0,a1,a2) op (b0,b1,b2) to
-// `IF( (a0 op b0) EQ 0, 0,
-//      IF ( (a1 op b1) EQ 0, 0, a2 op b2))`
-// 3. If op are LT or GT, constructBinaryOpFunctions converts (a0,a1,a2) op (b0,b1,b2) to
+// 2. Else constructBinaryOpFunctions converts (a0,a1,a2) op (b0,b1,b2) to
 // `IF( a0 NE b0, a0 op b0,
-//      IF( a1 NE b1,
-//          a1 op b1,
-//          a2 op b2)
-// )`
+// 		IF ( isNull(a0 NE b0), Null,
+// 			IF ( a1 NE b1, a1 op b1,
+// 				IF ( isNull(a1 NE b1), Null, a2 op b2))))`
 func (er *expressionRewriter) constructBinaryOpFunction(l expression.Expression, r expression.Expression, op string) (expression.Expression, error) {
 	lLen, rLen := expression.GetRowLen(l), expression.GetRowLen(r)
 	if lLen == 1 && rLen == 1 {
@@ -202,9 +198,10 @@ func (er *expressionRewriter) constructBinaryOpFunction(l expression.Expression,
 		return expression.ComposeCNFCondition(er.ctx, funcs...), nil
 	default:
 		larg0, rarg0 := expression.GetFuncArg(l, 0), expression.GetFuncArg(r, 0)
-		var expr1, expr2, expr3 expression.Expression
+		var expr1, expr2, expr3, expr4, expr5 expression.Expression
 		expr1 = expression.NewFunctionInternal(er.ctx, ast.NE, types.NewFieldType(mysql.TypeTiny), larg0, rarg0)
 		expr2 = expression.NewFunctionInternal(er.ctx, op, types.NewFieldType(mysql.TypeTiny), larg0, rarg0)
+		expr3 = expression.NewFunctionInternal(er.ctx, ast.IsNull, types.NewFieldType(mysql.TypeTiny), expr1)
 		var err error
 		l, err = expression.PopRowFirstArg(er.ctx, l)
 		if err != nil {
@@ -214,23 +211,15 @@ func (er *expressionRewriter) constructBinaryOpFunction(l expression.Expression,
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
-		if evalexpr, ok := expr1.(*expression.Constant); ok {
-			_, isNull, err1 := evalexpr.EvalInt(er.ctx, chunk.Row{})
-			if err1 != nil || isNull {
-				return expr1, err1
-			}
-		}
-		if evalexpr, ok := expr2.(*expression.Constant); ok {
-			_, isNull, err1 := evalexpr.EvalInt(er.ctx, chunk.Row{})
-			if err1 != nil || isNull {
-				return expr2, err1
-			}
+		expr4, err = er.constructBinaryOpFunction(l, r, op)
+		if err != nil {
+			return nil, errors.Trace(err)
 		}
-		expr3, err = er.constructBinaryOpFunction(l, r, op)
+		expr5, err = expression.NewFunction(er.ctx, ast.If, types.NewFieldType(mysql.TypeTiny), expr3, expression.Null, expr4)
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
-		return expression.NewFunction(er.ctx, ast.If, types.NewFieldType(mysql.TypeTiny), expr1, expr2, expr3)
+		return expression.NewFunction(er.ctx, ast.If, types.NewFieldType(mysql.TypeTiny), expr1, expr2, expr5)
 	}
 }
 

planner/core/expression_rewriter_test.go

@@ -41,3 +41,20 @@ func (s *testExpressionRewriterSuite) TestIfNullEliminateColName(c *C) {
 	fields := rs.Fields()
 	c.Assert(fields[0].Column.Name.L, Equals, "ifnull(a,b)")
 }
+
+func (s *testExpressionRewriterSuite) TestBinaryOpFunction(c *C) {
+	defer testleak.AfterTest(c)()
+	store, dom, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	tk := testkit.NewTestKit(c, store)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("CREATE TABLE t(a int, b int, c int);")
+	tk.MustExec("INSERT INTO t VALUES (1, 2, 3), (NULL, 2, 3  ), (1, NULL, 3),(1, 2,   NULL),(NULL, 2, 3+1), (1, NULL, 3+1), (1, 2+1, NULL),(NULL, 2, 3-1), (1, NULL, 3-1), (1, 2-1, NULL)")
+	tk.MustQuery("SELECT * FROM t WHERE (a,b,c) <= (1,2,3) order by b").Check(testkit.Rows("1 1 <nil>", "1 2 3"))
+	tk.MustQuery("SELECT * FROM t WHERE (a,b,c) > (1,2,3) order by b").Check(testkit.Rows("1 3 <nil>"))
+}