/
sort.go
194 lines (168 loc) · 4.55 KB
/
sort.go
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// Copyright 2020-2021 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package plan
import (
"fmt"
"io"
"sort"
"strings"
"github.com/Ciyfly/FakerMysql/sql"
"github.com/Ciyfly/FakerMysql/sql/expression"
)
// Sort is the sort node.
type Sort struct {
UnaryNode
SortFields []sql.SortField
}
// NewSort creates a new Sort node.
func NewSort(sortFields []sql.SortField, child sql.Node) *Sort {
return &Sort{
UnaryNode: UnaryNode{child},
SortFields: sortFields,
}
}
var _ sql.Expressioner = (*Sort)(nil)
// Resolved implements the Resolvable interface.
func (s *Sort) Resolved() bool {
for _, f := range s.SortFields {
if !f.Column.Resolved() {
return false
}
}
return s.Child.Resolved()
}
// RowIter implements the Node interface.
func (s *Sort) RowIter(ctx *sql.Context, row sql.Row) (sql.RowIter, error) {
span, ctx := ctx.Span("plan.Sort")
i, err := s.UnaryNode.Child.RowIter(ctx, row)
if err != nil {
span.Finish()
return nil, err
}
return sql.NewSpanIter(span, newSortIter(ctx, s, i)), nil
}
func (s *Sort) String() string {
pr := sql.NewTreePrinter()
var fields = make([]string, len(s.SortFields))
for i, f := range s.SortFields {
fields[i] = fmt.Sprintf("%s %s", f.Column, f.Order)
}
_ = pr.WriteNode("Sort(%s)", strings.Join(fields, ", "))
_ = pr.WriteChildren(s.Child.String())
return pr.String()
}
func (s *Sort) DebugString() string {
pr := sql.NewTreePrinter()
var fields = make([]string, len(s.SortFields))
for i, f := range s.SortFields {
fields[i] = sql.DebugString(f)
}
_ = pr.WriteNode("Sort(%s)", strings.Join(fields, ", "))
_ = pr.WriteChildren(sql.DebugString(s.Child))
return pr.String()
}
// Expressions implements the Expressioner interface.
func (s *Sort) Expressions() []sql.Expression {
// TODO: use shared method
var exprs = make([]sql.Expression, len(s.SortFields))
for i, f := range s.SortFields {
exprs[i] = f.Column
}
return exprs
}
// WithChildren implements the Node interface.
func (s *Sort) WithChildren(children ...sql.Node) (sql.Node, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(s, len(children), 1)
}
return NewSort(s.SortFields, children[0]), nil
}
// WithExpressions implements the Expressioner interface.
func (s *Sort) WithExpressions(exprs ...sql.Expression) (sql.Node, error) {
if len(exprs) != len(s.SortFields) {
return nil, sql.ErrInvalidChildrenNumber.New(s, len(exprs), len(s.SortFields))
}
var fields = make([]sql.SortField, len(s.SortFields))
for i, expr := range exprs {
fields[i] = sql.SortField{
Column: expr,
NullOrdering: s.SortFields[i].NullOrdering,
Order: s.SortFields[i].Order,
}
}
return NewSort(fields, s.Child), nil
}
type sortIter struct {
ctx *sql.Context
s *Sort
childIter sql.RowIter
sortedRows []sql.Row
idx int
}
func newSortIter(ctx *sql.Context, s *Sort, child sql.RowIter) *sortIter {
return &sortIter{
ctx: ctx,
s: s,
childIter: child,
idx: -1,
}
}
func (i *sortIter) Next() (sql.Row, error) {
if i.idx == -1 {
err := i.computeSortedRows()
if err != nil {
return nil, err
}
i.idx = 0
}
if i.idx >= len(i.sortedRows) {
return nil, io.EOF
}
row := i.sortedRows[i.idx]
i.idx++
return row, nil
}
func (i *sortIter) Close(ctx *sql.Context) error {
i.sortedRows = nil
return i.childIter.Close(ctx)
}
func (i *sortIter) computeSortedRows() error {
cache, dispose := i.ctx.Memory.NewRowsCache()
defer dispose()
for {
row, err := i.childIter.Next()
if err == io.EOF {
break
}
if err != nil {
return err
}
if err := cache.Add(row); err != nil {
return err
}
}
rows := cache.Get()
sorter := &expression.Sorter{
SortFields: i.s.SortFields,
Rows: rows,
LastError: nil,
Ctx: i.ctx,
}
sort.Stable(sorter)
if sorter.LastError != nil {
return sorter.LastError
}
i.sortedRows = rows
return nil
}