mirror of https://gitee.com/bigwinds/arangodb
87 lines
3.0 KiB
C++
87 lines
3.0 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
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/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
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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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///
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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Jan Steemann
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/// @author Daniel H. Larkin
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/// @author Simon Grätzer
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGO_ROCKSDB_ROCKSDB_PREFIX_EXTRACTOR_H
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#define ARANGO_ROCKSDB_ROCKSDB_PREFIX_EXTRACTOR_H 1
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#include "Basics/Common.h"
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#include <rocksdb/slice.h>
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#include <rocksdb/slice_transform.h>
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#include <velocypack/Slice.h>
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#include <velocypack/velocypack-aliases.h>
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namespace arangodb {
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/// @brief effectively used for the rocksdb edge index, to allow a
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/// dynamically length prefix spanning the indexed _from / _to string
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class RocksDBPrefixExtractor final : public rocksdb::SliceTransform {
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public:
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RocksDBPrefixExtractor() {}
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~RocksDBPrefixExtractor() = default;
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const char* Name() const override { return "RocksDBPrefixExtractor"; }
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rocksdb::Slice Transform(rocksdb::Slice const& key) const override {
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// 8-byte objectID + 0..n-byte string + 1-byte '\0'
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// + 8 byte revisionID + 1-byte 0xFF (these are for cut off)
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TRI_ASSERT(key.size() >= sizeof(char) + sizeof(uint64_t));
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if (key.data()[key.size() - 1] != '\0') {
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// unfortunately rocksdb seems to call Tranform(Transform(k))
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TRI_ASSERT(static_cast<uint8_t>(key.data()[key.size() - 1]) == 0xFFU);
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TRI_ASSERT(key.size() > sizeof(char) * 3 + sizeof(uint64_t) * 2);
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size_t l = key.size() - sizeof(uint64_t) - sizeof(char);
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TRI_ASSERT(key.data()[l - 1] == '\0');
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return rocksdb::Slice(key.data(), l);
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} else {
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TRI_ASSERT(key.data()[key.size() - 1] == '\0');
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return key;
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}
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}
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bool InDomain(rocksdb::Slice const& key) const override {
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// 8-byte objectID + n-byte string + 1-byte '\0' + ...
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TRI_ASSERT(key.size() >= sizeof(char) + sizeof(uint64_t));
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return key.data()[key.size() - 1] != '\0';
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}
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bool InRange(rocksdb::Slice const& dst) const override {
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TRI_ASSERT(dst.size() >= sizeof(char) + sizeof(uint64_t));
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return dst.data()[dst.size() - 1] != '\0';
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}
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bool SameResultWhenAppended(rocksdb::Slice const& prefix) const override {
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return prefix.data()[prefix.size() - 1] == '\0';
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}
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private:
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static const size_t _prefixLength[];
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};
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} // namespace arangodb
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#endif
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