planner: fix expression rewriter wrong compare logic (#8269) (#8288)

pingcap · Nov 13, 2018 · 162fa84 · 162fa84
1 parent 99837f5
commit 162fa84
Showing 1 changed file with 14 additions and 19 deletions.
diff --git a/plan/expression_rewriter.go b/plan/expression_rewriter.go
@@ -151,15 +151,11 @@ func popRowArg(ctx sessionctx.Context, e expression.Expression) (ret expression.
 }
 
 // 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 := getRowLen(l), getRowLen(r)
 	if lLen == 1 && rLen == 1 {
@@ -180,15 +176,10 @@ func (er *expressionRewriter) constructBinaryOpFunction(l expression.Expression,
 		return expression.ComposeCNFCondition(er.ctx, funcs...), nil
 	default:
 		larg0, rarg0 := getRowArg(l, 0), getRowArg(r, 0)
-		var expr1, expr2, expr3 expression.Expression
-		if op == ast.LE || op == ast.GE {
-			expr1 = expression.NewFunctionInternal(er.ctx, op, types.NewFieldType(mysql.TypeTiny), larg0, rarg0)
-			expr1 = expression.NewFunctionInternal(er.ctx, ast.EQ, types.NewFieldType(mysql.TypeTiny), expr1, expression.Zero)
-			expr2 = expression.Zero
-		} else if op == ast.LT || op == ast.GT {
-			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)
-		}
+		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 = popRowArg(er.ctx, l)
 		if err != nil {
@@ -198,11 +189,15 @@ func (er *expressionRewriter) constructBinaryOpFunction(l expression.Expression,
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
-		expr3, err = er.constructBinaryOpFunction(l, r, op)
+		expr4, err = er.constructBinaryOpFunction(l, r, op)
+		if err != nil {
+			return nil, errors.Trace(err)
+		}
+		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)
 	}
 }