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window.go
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window.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 sql
import (
"strings"
)
// A Window specifies the window parameters of a window function
type Window struct {
PartitionBy []Expression
OrderBy SortFields
// TODO: window frame
}
func NewWindow(partitionBy []Expression, orderBy []SortField) *Window {
return &Window{PartitionBy: partitionBy, OrderBy: orderBy}
}
// ToExpressions converts the PartitionBy and OrderBy expressions to a single slice of expressions suitable for
// manipulation by analyzer rules.
func (w *Window) ToExpressions() []Expression {
if w == nil {
return nil
}
return append(w.OrderBy.ToExpressions(), w.PartitionBy...)
}
// FromExpressions returns copy of this window with the given expressions taken to stand in for the partition and order
// by fields. An error is returned if the lengths or types of these expressions are incompatible with this window.
func (w *Window) FromExpressions(children []Expression) (*Window, error) {
if w == nil {
return nil, nil
}
if len(children) != len(w.OrderBy)+len(w.PartitionBy) {
return nil, ErrInvalidChildrenNumber.New(w, len(children), len(w.OrderBy)+len(w.PartitionBy))
}
nw := *w
nw.OrderBy = nw.OrderBy.FromExpressions(children[:len(nw.OrderBy)])
nw.PartitionBy = children[len(nw.OrderBy):]
return &nw, nil
}
func (w *Window) String() string {
if w == nil {
return ""
}
sb := strings.Builder{}
sb.WriteString("over (")
if len(w.PartitionBy) > 0 {
sb.WriteString(" partition by ")
for i, expression := range w.PartitionBy {
if i > 0 {
sb.WriteString(", ")
sb.WriteString(expression.String())
}
}
}
if len(w.OrderBy) > 0 {
sb.WriteString(" order by ")
for i, ob := range w.OrderBy {
if i > 0 {
sb.WriteString(", ")
}
sb.WriteString(ob.String())
}
}
sb.WriteString(")")
return sb.String()
}
func (w *Window) DebugString() string {
if w == nil {
return ""
}
sb := strings.Builder{}
sb.WriteString("over (")
if len(w.PartitionBy) > 0 {
sb.WriteString(" partition by ")
for i, expression := range w.PartitionBy {
if i > 0 {
sb.WriteString(", ")
}
sb.WriteString(DebugString(expression))
}
}
if len(w.OrderBy) > 0 {
sb.WriteString(" order by ")
for i, ob := range w.OrderBy {
if i > 0 {
sb.WriteString(", ")
}
sb.WriteString(DebugString(ob))
}
}
sb.WriteString(")")
return sb.String()
}