Merge pull request pingcap#876 from pingcap/shenli/agg-cleanup

*: Aggregate related code clean up

ast/functions.go

@@ -421,14 +421,14 @@ func (n *AggregateFuncExpr) Update() error {
 		return n.updateCount()
 	case AggFuncFirstRow:
 		return n.updateFirstRow()
+	case AggFuncGroupConcat:
+		return n.updateGroupConcat()
 	case AggFuncMax:
 		return n.updateMaxMin(true)
 	case AggFuncMin:
 		return n.updateMaxMin(false)
 	case AggFuncSum, AggFuncAvg:
 		return n.updateSum()
-	case AggFuncGroupConcat:
-		return n.updateGroupConcat()
 	}
 	return nil
 }

optimizer/optimizer.go

@@ -119,6 +119,7 @@ const (
 	CodeMultiWildCard       terror.ErrCode = 3
 	CodeUnsupported         terror.ErrCode = 4
 	CodeInvalidGroupFuncUse terror.ErrCode = 5
+	CodeIllegalReference    terror.ErrCode = 6
 )
 
 // Optimizer base errors.
@@ -128,6 +129,7 @@ var (
 	ErrMultiWildCard       = terror.ClassOptimizer.New(CodeMultiWildCard, "wildcard field exist more than once")
 	ErrUnSupported         = terror.ClassOptimizer.New(CodeUnsupported, "unsupported")
 	ErrInvalidGroupFuncUse = terror.ClassOptimizer.New(CodeInvalidGroupFuncUse, "Invalid use of group function")
+	ErrIllegalReference    = terror.ClassOptimizer.New(CodeIllegalReference, "Illegal reference")
 )
 
 func init() {
@@ -136,6 +138,7 @@ func init() {
 		CodeSameColumns:         mysql.ErrOperandColumns,
 		CodeMultiWildCard:       mysql.ErrParse,
 		CodeInvalidGroupFuncUse: mysql.ErrInvalidGroupFuncUse,
+		CodeIllegalReference:    mysql.ErrIllegalReference,
 	}
 	terror.ErrClassToMySQLCodes[terror.ClassOptimizer] = mySQLErrCodes
 }

optimizer/resolver.go

@@ -136,7 +136,7 @@ func (nr *nameResolver) Enter(inNode ast.Node) (outNode ast.Node, skipChildren b
 		if nr.currentContext().inGroupBy {
 			// make sure item is not aggregate function
 			if ast.HasAggFlag(v.Expr) {
-				nr.Err = errors.New("group by cannot contain aggregate function")
+				nr.Err = ErrInvalidGroupFuncUse
 				return inNode, true
 			}
 		}
@@ -326,12 +326,13 @@ func (nr *nameResolver) resolveColumnNameInContext(ctx *resolverContext, cn *ast
 				return true
 			}
 			found := nr.resolveColumnInResultFields(ctx, cn, ctx.fieldList)
-			if !found || nr.Err != nil {
-				return found
-			}
-			if _, ok := cn.Refer.Expr.(*ast.AggregateFuncExpr); ok {
-				nr.Err = errors.New("Groupby identifier can not refer to aggregate function.")
+			if nr.Err == nil && found {
+				// Check if resolved refer is an aggregate function expr.
+				if _, ok := cn.Refer.Expr.(*ast.AggregateFuncExpr); ok {
+					nr.Err = ErrIllegalReference.Gen("Reference '%s' not supported (reference to group function)", cn.Name.Name.O)
+				}
 			}
+			return found
 		}
 		// Resolve from table first, then from select list.
 		found := nr.resolveColumnInTableSources(cn, ctx.tables)
@@ -353,7 +354,7 @@ func (nr *nameResolver) resolveColumnNameInContext(ctx *resolverContext, cn *ast
 				cn.Refer = r
 			}
 			if _, ok := cn.Refer.Expr.(*ast.AggregateFuncExpr); ok {
-				nr.Err = errors.New("Groupby identifier can not refer to aggregate function.")
+				nr.Err = ErrIllegalReference.Gen("Reference '%s' not supported (reference to group function)", cn.Name.Name.O)
 			}
 			return true
 		}