/
rank.go
115 lines (95 loc) · 2.75 KB
/
rank.go
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// Copyright 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 window
import (
"strings"
"github.com/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/expression/function/aggregation"
)
type Rank struct {
window *sql.WindowDefinition
pos int
}
var _ sql.FunctionExpression = (*Rank)(nil)
var _ sql.WindowAggregation = (*Rank)(nil)
var _ sql.WindowAdaptableExpression = (*Rank)(nil)
func NewRank() sql.Expression {
return &Rank{}
}
// Description implements sql.FunctionExpression
func (p *Rank) Description() string {
return "returns rank value."
}
// Window implements sql.WindowExpression
func (p *Rank) Window() *sql.WindowDefinition {
return p.window
}
func (p *Rank) Resolved() bool {
return windowResolved(p.window)
}
func (p *Rank) String() string {
sb := strings.Builder{}
sb.WriteString("rank()")
if p.window != nil {
sb.WriteString(" ")
sb.WriteString(p.window.String())
}
return sb.String()
}
func (p *Rank) DebugString() string {
sb := strings.Builder{}
sb.WriteString("rank()")
if p.window != nil {
sb.WriteString(" ")
sb.WriteString(sql.DebugString(p.window))
}
return sb.String()
}
// FunctionName implements sql.FunctionExpression
func (p *Rank) FunctionName() string {
return "RANK"
}
// Type implements sql.Expression
func (p *Rank) Type() sql.Type {
return sql.Uint64
}
// IsNullable implements sql.Expression
func (p *Rank) IsNullable() bool {
return false
}
// Eval implements sql.Expression
func (p *Rank) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
panic("eval called on window function")
}
// Children implements sql.Expression
func (p *Rank) Children() []sql.Expression {
return p.window.ToExpressions()
}
// WithChildren implements sql.Expression
func (p *Rank) WithChildren(children ...sql.Expression) (sql.Expression, error) {
window, err := p.window.FromExpressions(children)
if err != nil {
return nil, err
}
return p.WithWindow(window)
}
// WithWindow implements sql.WindowAggregation
func (p *Rank) WithWindow(window *sql.WindowDefinition) (sql.WindowAggregation, error) {
nr := *p
nr.window = window
return &nr, nil
}
func (p *Rank) NewWindowFunction() (sql.WindowFunction, error) {
return aggregation.NewRank(p.window.OrderBy.ToExpressions()), nil
}