65 lines
1.9 KiB
Go
65 lines
1.9 KiB
Go
// 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 store
|
|
|
|
// At the moment this happens to be the same interface as described by
|
|
// RocksDB, but this may not always be the case.
|
|
|
|
type MergeOperator interface {
|
|
|
|
// FullMerge the full sequence of operands on top of the existingValue
|
|
// if no value currently exists, existingValue is nil
|
|
// return the merged value, and success/failure
|
|
FullMerge(key, existingValue []byte, operands [][]byte) ([]byte, bool)
|
|
|
|
// Partially merge these two operands.
|
|
// If partial merge cannot be done, return nil,false, which will defer
|
|
// all processing until the FullMerge is done.
|
|
PartialMerge(key, leftOperand, rightOperand []byte) ([]byte, bool)
|
|
|
|
// Name returns an identifier for the operator
|
|
Name() string
|
|
}
|
|
|
|
type EmulatedMerge struct {
|
|
Merges map[string][][]byte
|
|
mo MergeOperator
|
|
}
|
|
|
|
func NewEmulatedMerge(mo MergeOperator) *EmulatedMerge {
|
|
return &EmulatedMerge{
|
|
Merges: make(map[string][][]byte),
|
|
mo: mo,
|
|
}
|
|
}
|
|
|
|
func (m *EmulatedMerge) Merge(key, val []byte) {
|
|
ops, ok := m.Merges[string(key)]
|
|
if ok && len(ops) > 0 {
|
|
last := ops[len(ops)-1]
|
|
mergedVal, partialMergeOk := m.mo.PartialMerge(key, last, val)
|
|
if partialMergeOk {
|
|
// replace last entry with the result of the merge
|
|
ops[len(ops)-1] = mergedVal
|
|
} else {
|
|
// could not partial merge, append this to the end
|
|
ops = append(ops, val)
|
|
}
|
|
} else {
|
|
ops = [][]byte{val}
|
|
}
|
|
m.Merges[string(key)] = ops
|
|
}
|