本文整理汇总了Golang中github.com/pingcap/tidb/ast.SelectStmt.SetResultFields方法的典型用法代码示例。如果您正苦于以下问题：Golang SelectStmt.SetResultFields方法的具体用法？Golang SelectStmt.SetResultFields怎么用？Golang SelectStmt.SetResultFields使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类github.com/pingcap/tidb/ast.SelectStmt的用法示例。
在下文中一共展示了SelectStmt.SetResultFields方法的2个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的Golang代码示例。
示例1: extractSelectAgg
// 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
}示例2: extractSelectAgg
// 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
}