77 lines
2.1 KiB
Go
Vendored
77 lines
2.1 KiB
Go
Vendored
// Copyright (c) 2014 Couchbase, 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 upsidedown
|
|
|
|
import (
|
|
"encoding/binary"
|
|
)
|
|
|
|
var mergeOperator upsideDownMerge
|
|
|
|
var dictionaryTermIncr []byte
|
|
var dictionaryTermDecr []byte
|
|
|
|
func init() {
|
|
dictionaryTermIncr = make([]byte, 8)
|
|
binary.LittleEndian.PutUint64(dictionaryTermIncr, uint64(1))
|
|
dictionaryTermDecr = make([]byte, 8)
|
|
var negOne = int64(-1)
|
|
binary.LittleEndian.PutUint64(dictionaryTermDecr, uint64(negOne))
|
|
}
|
|
|
|
type upsideDownMerge struct{}
|
|
|
|
func (m *upsideDownMerge) FullMerge(key, existingValue []byte, operands [][]byte) ([]byte, bool) {
|
|
// set up record based on key
|
|
dr, err := NewDictionaryRowK(key)
|
|
if err != nil {
|
|
return nil, false
|
|
}
|
|
if len(existingValue) > 0 {
|
|
// if existing value, parse it
|
|
err = dr.parseDictionaryV(existingValue)
|
|
if err != nil {
|
|
return nil, false
|
|
}
|
|
}
|
|
|
|
// now process operands
|
|
for _, operand := range operands {
|
|
next := int64(binary.LittleEndian.Uint64(operand))
|
|
if next < 0 && uint64(-next) > dr.count {
|
|
// subtracting next from existing would overflow
|
|
dr.count = 0
|
|
} else if next < 0 {
|
|
dr.count -= uint64(-next)
|
|
} else {
|
|
dr.count += uint64(next)
|
|
}
|
|
}
|
|
|
|
return dr.Value(), true
|
|
}
|
|
|
|
func (m *upsideDownMerge) PartialMerge(key, leftOperand, rightOperand []byte) ([]byte, bool) {
|
|
left := int64(binary.LittleEndian.Uint64(leftOperand))
|
|
right := int64(binary.LittleEndian.Uint64(rightOperand))
|
|
rv := make([]byte, 8)
|
|
binary.LittleEndian.PutUint64(rv, uint64(left+right))
|
|
return rv, true
|
|
}
|
|
|
|
func (m *upsideDownMerge) Name() string {
|
|
return "upsideDownMerge"
|
|
}
|