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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 window
import (
"github.com/Rock-liyi/p2pdb-store/sql"
"github.com/Rock-liyi/p2pdb-store/sql/expression"
)
func windowResolved(window *sql.Window) bool {
if window == nil {
return true
}
return expression.ExpressionsResolved(append(window.OrderBy.ToExpressions(), window.PartitionBy...)...)
}
func partitionsToSortFields(partitionExprs []sql.Expression) sql.SortFields {
sfs := make(sql.SortFields, len(partitionExprs))
for i, expr := range partitionExprs {
sfs[i] = sql.SortField{
Column: expr,
Order: sql.Ascending,
}
}
return sfs
}
func evalExprs(ctx *sql.Context, exprs []sql.Expression, row sql.Row) (sql.Row, error) {
result := make(sql.Row, len(exprs))
for i, expr := range exprs {
var err error
result[i], err = expr.Eval(ctx, row)
if err != nil {
return nil, err
}
}
return result, nil
}
// isNewPartition compares the order by columns between two rows, returning true when the last row is null
// or when next row is in a different partition than the last
func isNewPartition(ctx *sql.Context, partitionBy []sql.Expression, last sql.Row, row sql.Row) (bool, error) {
if len(last) == 0 {
return true, nil
}
if len(partitionBy) == 0 {
return false, nil
}
lastExp, err := evalExprs(ctx, partitionBy, last)
if err != nil {
return false, err
}
thisExp, err := evalExprs(ctx, partitionBy, row)
if err != nil {
return false, err
}
for i := range lastExp {
if lastExp[i] != thisExp[i] {
return true, nil
}
}
return false, nil
}
// isNewOrderValue compares the order by columns between two rows, returning true when the last row is null or
// when the next row's orderBy columns are unique
func isNewOrderValue(ctx *sql.Context, orderByExprs []sql.Expression, last sql.Row, row sql.Row) (bool, error) {
if len(last) == 0 {
return true, nil
}
lastExp, err := evalExprs(ctx, orderByExprs, last)
if err != nil {
return false, err
}
thisExp, err := evalExprs(ctx, orderByExprs, row)
if err != nil {
return false, err
}
for i := range lastExp {
if lastExp[i] != thisExp[i] {
return true, nil
}
}
return false, nil
}