예제 #1
0
// extractSelectAgg extracts aggregate functions and converts ColumnNameExpr to aggregate function.
func (b *planBuilder) extractSelectAgg(sel *ast.SelectStmt) []*ast.AggregateFuncExpr {
	extractor := &ast.AggregateFuncExtractor{AggFuncs: make([]*ast.AggregateFuncExpr, 0)}
	res := make([]*ast.ResultField, 0, len(sel.GetResultFields()))
	for _, f := range sel.GetResultFields() {
		n, ok := f.Expr.Accept(extractor)
		if !ok {
			b.err = errors.New("Failed to extract agg expr!")
			return nil
		}
		ve, ok := f.Expr.(*ast.ValueExpr)
		if ok && len(f.Column.Name.O) > 0 {
			agg := &ast.AggregateFuncExpr{
				F:    ast.AggFuncFirstRow,
				Args: []ast.ExprNode{ve},
			}
			extractor.AggFuncs = append(extractor.AggFuncs, agg)
			n = agg
		}
		// Clone the ResultField.
		// For "select c from t group by c;" both "c"s in select field and grouby clause refer to the same ResultField.
		// So we should not affact the "c" in groupby clause.
		nf := &ast.ResultField{
			ColumnAsName: f.ColumnAsName,
			Column:       f.Column,
			Table:        f.Table,
			DBName:       f.DBName,
			Expr:         n.(ast.ExprNode),
		}
		res = append(res, nf)
	}
	sel.SetResultFields(res)
	// Extract agg funcs from having clause.
	if sel.Having != nil {
		n, ok := sel.Having.Expr.Accept(extractor)
		if !ok {
			b.err = errors.New("Failed to extract agg expr from having clause")
			return nil
		}
		sel.Having.Expr = n.(ast.ExprNode)
	}
	// Extract agg funcs from orderby clause.
	if sel.OrderBy != nil {
		for _, item := range sel.OrderBy.Items {
			n, ok := item.Expr.Accept(extractor)
			if !ok {
				b.err = errors.New("Failed to extract agg expr from orderby clause")
				return nil
			}
			item.Expr = n.(ast.ExprNode)
			// If item is PositionExpr, we need to rebind it.
			// For PositionExpr will refer to a ResultField in fieldlist.
			// After extract AggExpr from fieldlist, it may be changed (See the code above).
			if pe, ok := item.Expr.(*ast.PositionExpr); ok {
				pe.Refer = sel.GetResultFields()[pe.N-1]
			}
		}
	}
	return extractor.AggFuncs
}
예제 #2
0
파일: planbuilder.go 프로젝트: zxylvlp/tidb
// extractSelectAgg extracts aggregate functions and converts ColumnNameExpr to aggregate function.
func (b *planBuilder) extractSelectAgg(sel *ast.SelectStmt) []*ast.AggregateFuncExpr {
	extractor := &ast.AggregateFuncExtractor{AggFuncs: make([]*ast.AggregateFuncExpr, 0)}
	res := make([]*ast.ResultField, 0, len(sel.GetResultFields()))
	for _, f := range sel.GetResultFields() {
		n, ok := f.Expr.Accept(extractor)
		if !ok {
			b.err = errors.New("Failed to extract agg expr!")
			return nil
		}
		ve, ok := f.Expr.(*ast.ValueExpr)
		if ok && len(f.Column.Name.O) > 0 {
			agg := &ast.AggregateFuncExpr{
				F:    ast.AggFuncFirstRow,
				Args: []ast.ExprNode{ve},
			}
			extractor.AggFuncs = append(extractor.AggFuncs, agg)
			n = agg
		}
		// Clone the ResultField.
		// For "select c from t group by c;" both "c"s in select field and grouby clause refer to the same ResultField.
		// So we should not affact the "c" in groupby clause.
		nf := &ast.ResultField{
			ColumnAsName: f.ColumnAsName,
			Column:       f.Column,
			Table:        f.Table,
			DBName:       f.DBName,
			Expr:         n.(ast.ExprNode),
		}
		res = append(res, nf)
	}
	sel.SetResultFields(res)
	// Extract agg funcs from orderby clause.
	if sel.OrderBy != nil {
		for _, item := range sel.OrderBy.Items {
			n, ok := item.Expr.Accept(extractor)
			if !ok {
				b.err = errors.New("Failed to extract agg expr from orderby clause")
				return nil
			}
			item.Expr = n.(ast.ExprNode)
		}
	}
	// TODO: extract aggfuncs from having clause.
	return extractor.AggFuncs
}