60 lines
1.9 KiB
Go
60 lines
1.9 KiB
Go
// Copyright (c) 2014 Couchbase, Inc.
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
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// except in compliance with the License. You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed under the
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// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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// either express or implied. See the License for the specific language governing permissions
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// and limitations under the License.
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package store
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// At the moment this happens to be the same interface as described by
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// RocksDB, but this may not always be the case.
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type MergeOperator interface {
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// FullMerge the full sequence of operands on top of the existingValue
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// if no value currently exists, existingValue is nil
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// return the merged value, and success/failure
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FullMerge(key, existingValue []byte, operands [][]byte) ([]byte, bool)
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// Partially merge these two operands.
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// If partial merge cannot be done, return nil,false, which will defer
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// all processing until the FullMerge is done.
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PartialMerge(key, leftOperand, rightOperand []byte) ([]byte, bool)
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// Name returns an identifier for the operator
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Name() string
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}
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type EmulatedMerge struct {
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Merges map[string][][]byte
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mo MergeOperator
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}
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func NewEmulatedMerge(mo MergeOperator) *EmulatedMerge {
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return &EmulatedMerge{
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Merges: make(map[string][][]byte),
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mo: mo,
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}
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}
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func (m *EmulatedMerge) Merge(key, val []byte) {
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ops, ok := m.Merges[string(key)]
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if ok && len(ops) > 0 {
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last := ops[len(ops)-1]
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mergedVal, partialMergeOk := m.mo.PartialMerge(key, last, val)
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if partialMergeOk {
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// replace last entry with the result of the merge
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ops[len(ops)-1] = mergedVal
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} else {
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// could not partial merge, append this to the end
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ops = append(ops, val)
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}
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} else {
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ops = [][]byte{val}
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}
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m.Merges[string(key)] = ops
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}
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