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DependentExtensions/cat/db/BombayTableIndex.hpp
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DependentExtensions/cat/db/BombayTableIndex.hpp
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/*
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Copyright (c) 2009-2010 Christopher A. Taylor. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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* Neither the name of LibCat nor the names of its contributors may be used
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to endorse or promote products derived from this software without
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specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef CAT_BOMBAY_TABLE_INDEX_HPP
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#define CAT_BOMBAY_TABLE_INDEX_HPP
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#include <cat/db/BombayTable.hpp>
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namespace cat {
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namespace bombay {
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/*
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Returning 0 from one of these hash functions will cause insertion or lookup to fail,
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which is how invalid input is intended to be handled.
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*/
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class IHash
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{
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public:
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virtual u64 HashField(const void *just_field) = 0;
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virtual u64 HashComplete(const void *complete_record) = 0;
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virtual u64 HashVarField(const void *just_field, u32 bytes) { return HashField(just_field); }
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};
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#define DECL_BOMBAY_SCHEMA_VAR_FIELD_HASH(T) \
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class T : public bombay::IHash \
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{ \
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public: \
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u64 HashField(const void *just_field); \
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u64 HashComplete(const void *complete_record); \
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u64 HashVarField(const void *just_field, u32 bytes); \
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};
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#define DECL_BOMBAY_SCHEMA_FIXED_FIELD_HASH(T) \
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class T : public bombay::IHash \
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{ \
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public: \
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u64 HashField(const void *just_field); \
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u64 HashComplete(const void *complete_record); \
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};
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/*
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Table index must present a complete index of the contents of a Table.
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The index uses some region of bytes in each entry as a key to find
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the entry given just that set of bytes. For example, mapping a user
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name to a database node.
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The table index should be loaded from disk on startup. If this is
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not possible, then an index rebuild will need to be done on startup.
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Hash table size will be at least twice as large as the number of
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database entries, growing as needed.
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To avoid a lot of expensive setup, each element is arranged like this:
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<-- MSB LSB -->
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C(1 bit) || OFFSET+1 (63 bits)
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HASH(64 bits)
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C: Collision flag
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0 = No collision
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1 = Collision, actual data may be stored at next walk location
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OFFSET+1: Database file offset for this entry that contains the
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full unique identifier. One(1) is added to the offset in
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the memory representation of the index table element, so that
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OFFSET = ~0 will be set by zeroing out the table.
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0 = No data at this table element.
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Other values = Valid offset+1
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HASH: 64-bit full hash
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Only low bits are used for table lookup, so hash does not need
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to be recomputed if the table grows and lookup of something that
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is not in the table does not have collisions half the time.
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The whole structure fits in one cache line on an x86 server.
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*/
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class Table;
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class TableIndex : public AsyncFile
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{
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friend class Table;
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ShutdownObserver *_shutdown_observer;
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Table *_parent;
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IHash *_index_hash;
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TableIndex *_next, *_next_unique, *_next_loading;
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protected:
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// (multiplier-1) divisible by all prime factors of table size
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// (multiplier-1) is a multiple of 4 if table size is a multiple of 4
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// Increment is relatively prime to the table size.
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static const u32 COLLISION_MULTIPLIER = 71*7487 * 4 + 1;
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static const u32 COLLISION_INCREMENTER = 1017234223;
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static const u64 OFFSET_MASK = (~(u64)0) >> 1;
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static const u64 COLLIDE_MASK = ~OFFSET_MASK;
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static const u32 MIN_ELEMENTS = 1024;
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static const u32 TABLE_FOOTER_BYTES = 16;
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static const u64 TABLE_CHECK_HASH_SALT = 0x74B1301234DEADBE;
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RWLock _lock;
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u64 *_table;
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u32 _table_raw_bytes;
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u32 _table_elements; // A power of 2; just subtract 1 to make a mask
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u32 _used_elements;
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char _file_path[MAX_PATH+1];
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bool AllocateTable();
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bool DoubleTable();
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void FreeTable();
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protected:
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void Save();
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public:
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TableIndex(Table *parent, const char *index_file_path,
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IHash *hash_function, ShutdownObserver *shutdown_observer);
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~TableIndex();
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bool Initialize();
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protected:
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virtual bool OnRead(ThreadPoolLocalStorage *tls, int error, AsyncBuffer *buffer, u32 bytes);
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public:
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CAT_INLINE const char *GetFilePath() { return _file_path; }
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public:
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CAT_INLINE u64 VarField(const void *data, u32 bytes)
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{
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return _index_hash->HashVarField(data, bytes);
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}
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CAT_INLINE u64 Field(const void *data)
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{
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return _index_hash->HashField(data);
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}
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CAT_INLINE u64 Complete(const void *data)
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{
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return _index_hash->HashComplete(data);
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}
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public:
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// Hash value of 0 will be ignored
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u64 Lookup(u64 hash);
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void Insert(u64 hash, u64 offset);
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void Remove(u64 hash);
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public:
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CAT_INLINE u64 LookupVarField(const void *data, u32 bytes)
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{
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return Lookup(_index_hash->HashVarField(data, bytes));
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}
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CAT_INLINE u64 LookupField(const void *data)
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{
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return Lookup(_index_hash->HashField(data));
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}
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CAT_INLINE u64 LookupComplete(const void *data)
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{
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return Lookup(_index_hash->HashComplete(data));
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}
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public:
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CAT_INLINE void InsertVarField(const void *data, u32 bytes, u64 offset)
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{
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Insert(_index_hash->HashVarField(data, bytes), offset);
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}
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CAT_INLINE void InsertField(const void *data, u64 offset)
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{
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Insert(_index_hash->HashField(data), offset);
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}
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CAT_INLINE void InsertComplete(const void *data, u64 offset)
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{
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Insert(_index_hash->HashComplete(data), offset);
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}
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public:
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CAT_INLINE void RemoveVarField(const void *data, u32 bytes)
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{
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Remove(_index_hash->HashVarField(data, bytes));
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}
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CAT_INLINE void RemoveField(const void *data)
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{
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Remove(_index_hash->HashField(data));
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}
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CAT_INLINE void RemoveComplete(const void *data)
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{
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Remove(_index_hash->HashComplete(data));
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}
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};
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} // namespace bombay
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} // namespace cat
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#endif // CAT_BOMBAY_TABLE_INDEX_HPP
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