77 lines
2.1 KiB
Go
77 lines
2.1 KiB
Go
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// Copyright (c) 2014 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package upsidedown
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import (
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"encoding/binary"
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)
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var mergeOperator upsideDownMerge
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var dictionaryTermIncr []byte
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var dictionaryTermDecr []byte
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func init() {
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dictionaryTermIncr = make([]byte, 8)
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binary.LittleEndian.PutUint64(dictionaryTermIncr, uint64(1))
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dictionaryTermDecr = make([]byte, 8)
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var negOne = int64(-1)
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binary.LittleEndian.PutUint64(dictionaryTermDecr, uint64(negOne))
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}
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type upsideDownMerge struct{}
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func (m *upsideDownMerge) FullMerge(key, existingValue []byte, operands [][]byte) ([]byte, bool) {
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// set up record based on key
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dr, err := NewDictionaryRowK(key)
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if err != nil {
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return nil, false
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}
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if len(existingValue) > 0 {
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// if existing value, parse it
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err = dr.parseDictionaryV(existingValue)
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if err != nil {
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return nil, false
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}
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}
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// now process operands
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for _, operand := range operands {
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next := int64(binary.LittleEndian.Uint64(operand))
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if next < 0 && uint64(-next) > dr.count {
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// subtracting next from existing would overflow
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dr.count = 0
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} else if next < 0 {
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dr.count -= uint64(-next)
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} else {
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dr.count += uint64(next)
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}
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}
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return dr.Value(), true
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}
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func (m *upsideDownMerge) PartialMerge(key, leftOperand, rightOperand []byte) ([]byte, bool) {
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left := int64(binary.LittleEndian.Uint64(leftOperand))
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right := int64(binary.LittleEndian.Uint64(rightOperand))
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rv := make([]byte, 8)
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binary.LittleEndian.PutUint64(rv, uint64(left+right))
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return rv, true
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}
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func (m *upsideDownMerge) Name() string {
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return "upsideDownMerge"
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}
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