planner/core: correct column name with unary plus sign (#8702)

Author: zyguan

cmd/explaintest/r/select.result

@@ -137,7 +137,7 @@ select !(1 + 2);
 !(1 + 2)
 0
 select + - 1, --1, +-+-+1, + "123";
-+ - 1	--1	+-+-+1	+ "123"
++ - 1	--1	+-+-+1	123
 -1	1	1	123
 select --------------------1, ++++++++++++++++++++1;
 --------------------1	++++++++++++++++++++1

executor/executor_test.go

@@ -1954,6 +1954,15 @@ func (s *testSuite) TestColumnName(c *C) {
 	c.Check(fields[0].Table.Name.L, Equals, "")
 	c.Check(fields[0].TableAsName.L, Equals, "")
 	c.Check(fields[0].DBName.L, Equals, "")
+	// Test case for query a column wrapped with parentheses and unary plus.
+	// In this case, the column name should be its original name.
+	rs, err = tk.Exec("select (c), (+c), +(c), +(+(c)), ++c from t")
+	c.Check(err, IsNil)
+	fields = rs.Fields()
+	for i := 0; i < 5; i++ {
+		c.Check(fields[0].Column.Name.L, Equals, "c")
+		c.Check(fields[0].ColumnAsName.L, Equals, "c")
+	}
 }
 
 func (s *testSuite) TestSelectVar(c *C) {

planner/core/logical_plan_builder.go

@@ -513,7 +513,7 @@ func (b *PlanBuilder) buildSelection(p LogicalPlan, where ast.ExprNode, AggMappe
 
 // buildProjectionFieldNameFromColumns builds the field name, table name and database name when field expression is a column reference.
 func (b *PlanBuilder) buildProjectionFieldNameFromColumns(field *ast.SelectField, c *expression.Column) (colName, origColName, tblName, origTblName, dbName model.CIStr) {
-	if astCol, ok := getInnerFromParentheses(field.Expr).(*ast.ColumnNameExpr); ok {
+	if astCol, ok := getInnerFromParenthesesAndUnaryPlus(field.Expr).(*ast.ColumnNameExpr); ok {
 		origColName, tblName, dbName = astCol.Name.Name, astCol.Name.Table, astCol.Name.Schema
 	}
 	if field.AsName.L != "" {
@@ -537,7 +537,7 @@ func (b *PlanBuilder) buildProjectionFieldNameFromExpressions(field *ast.SelectF
 		return agg.Args[0].(*ast.ColumnNameExpr).Name.Name
 	}
 
-	innerExpr := getInnerFromParentheses(field.Expr)
+	innerExpr := getInnerFromParenthesesAndUnaryPlus(field.Expr)
 	valueExpr, isValueExpr := innerExpr.(*driver.ValueExpr)
 
 	// Non-literal: Output as inputed, except that comments need to be removed.
@@ -2468,9 +2468,12 @@ func appendVisitInfo(vi []visitInfo, priv mysql.PrivilegeType, db, tbl, col stri
 	})
 }
 
-func getInnerFromParentheses(expr ast.ExprNode) ast.ExprNode {
+func getInnerFromParenthesesAndUnaryPlus(expr ast.ExprNode) ast.ExprNode {
 	if pexpr, ok := expr.(*ast.ParenthesesExpr); ok {
-		return getInnerFromParentheses(pexpr.Expr)
+		return getInnerFromParenthesesAndUnaryPlus(pexpr.Expr)
+	}
+	if uexpr, ok := expr.(*ast.UnaryOperationExpr); ok && uexpr.Op == opcode.Plus {
+		return getInnerFromParenthesesAndUnaryPlus(uexpr.V)
 	}
 	return expr
 }