324 lines
6.9 KiB
C++
324 lines
6.9 KiB
C++
/*
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----
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This file is part of SECONDO.
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Copyright (C) 2009, University in Hagen, Faculty of Mathematics and Computer Science,
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Database Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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SECONDO is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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1 Header File TupleBuffer2.h
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June 2009, Sven Jungnickel. Initial version.
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2 Overview
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Class ~TupleBuffer2~ is a replacement for the class
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~TupleBuffer~ in RelationAlgebra. As the former ~TupleBuffer~
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has been implemented as a subclass of ~GenericRelation~, which
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also allows random access, we have decided to implement the
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~TupleBuffer2~ class as a separate new class. The main
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differences are
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* Allows only sequential access
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* If the internal buffer overflows not the whole buffer is flushed
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to disk, but only the amount of tuples that caused the overflow. Thus
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tuples are moved gradually to disk following the FIFO principle.
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* Tuples moved to disk are stored in a temporary ~TupleFile~ (see
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RelationAlgebra.h for details)
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3 Defines, includes, and constants
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*/
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#ifndef TUPLEBUFFER2_H_
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#define TUPLEBUFFER2_H_
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#include <queue>
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#include "Algebras/Relation-C++/RelationAlgebra.h"
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#include "RTuple.h"
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/*
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In order to avoid name conflicts and to simplify replacement
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~TupleBuffer2~ has been placed in the namespace ~extrel2~.
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*/
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namespace extrel2
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{
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class TupleBuffer2;
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/*
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Necessary forward declaration for class ~TupleBuffer2Iterator~.
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*/
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/*
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4 Class ~TupleBuffer2Iterator~
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~TupleBuffer2Iterator~ is used to scan a ~TupleBuffer2~ instance
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sequentially.
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*/
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class TupleBuffer2Iterator
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{
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public:
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TupleBuffer2Iterator(TupleBuffer2& buffer);
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/*
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The constructor. Initializes a sequential scan of ~buffer~.
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A scan always starts with the tuples located on disk and then
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proceeds through the in-memory tuples.
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*/
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~TupleBuffer2Iterator();
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/*
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The destructor.
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*/
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Tuple* GetNextTuple();
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/*
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Returns a pointer to the next tuple from the ~TupleBuffer2~ instance.
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If all tuples have been processed 0 is returned.
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*/
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private:
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TupleBuffer2& tupleBuffer;
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/*
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Reference to ~TupleBuffer2~ instance.
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*/
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TupleFileIterator* iterDiskBuffer;
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/*
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~TupleFileIterator~ for disk buffer.
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*/
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std::vector<RTuple>::iterator iterMemoryBuffer;
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/*
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Iterator for in-memory array ~memoryBufferCopy~.
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*/
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std::vector<RTuple> memoryBufferCopy;
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/*
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Copy of the FIFO queue content of the ~TupleBuffer2~
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instance. The copy is made when the Iterator is
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constructed. The copy is necessary because the
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used queue implementation by ~TupleBuffer2~ is based
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on a STL queue, which does not support iteration.
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*/
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};
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/*
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5 Class ~TupleBuffer2~
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*/
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class TupleBuffer2
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{
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public:
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TupleBuffer2( const size_t maxMemorySize = 16 * 1024 * 1024,
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const size_t ioBufferSize = WinUnix::getPageSize() );
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/*
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First constructor. Constructs an instance with ~maxMemorySize~ bytes of
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internal memory. The I/O buffer size for read/write operations on
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disk is set to ~ioBufferSize~. The filename for the ~diskBuffer~ will
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be generated automatically.
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*/
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TupleBuffer2( const std::string& pathName,
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const size_t maxMemorySize = 16 * 1024 * 1024,
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const size_t ioBufferSize = WinUnix::getPageSize() );
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/*
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Second constructor. Constructs an instance with a specific filename
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~pathName~ for the external buffer and ~maxMemorySize~ bytes of
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internal memory. The I/O buffer size for read/write operations on
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disk is set to ~ioBufferSize~.
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*/
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~TupleBuffer2();
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/*
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The destructor.
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*/
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void Clear();
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/*
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Cleans the internal and external buffers.
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*/
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void CloseDiskBuffer();
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/*
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Closes the external buffer of type ~TupleFile~ if open.
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*/
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inline int GetNoTuples() const
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{
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if ( diskBuffer != 0 )
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{
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return ( (int)memoryBuffer.size() + diskBuffer->GetNoTuples() );
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}
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else
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{
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return (int)memoryBuffer.size();
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}
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}
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/*
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Returns the number of tuples within the internal and external buffers.
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*/
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inline size_t GetTotalExtSize() const { return totalExtSize; };
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/*
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Returns the total size of the extension part of all tuples
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within the internal and external buffers.
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*/
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inline size_t GetTotalSize() const { return totalSize; };
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/*
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Returns the total size of all tuples within the internal and
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external buffers.
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*/
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void AppendTuple( Tuple *t );
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/*
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Append tuple ~t~ to the buffer.
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*/
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TupleBuffer2Iterator* MakeScan();
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/*
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Start a sequential scan of the tuples in the buffer.
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*/
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bool IsEmpty() const { return inMemory ? memoryBuffer.empty() : false; }
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/*
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Returns true if the buffer is empty, otherwise false.
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*/
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inline size_t FreeBytes() const
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{ return inMemory ? ( MAX_MEMORY_SIZE - totalSize ) : 0; }
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/*
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Returns the number of free bytes in the internal buffer.
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*/
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inline bool InMemory() const { return inMemory; }
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/*
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Returns true if all tuples are in the internal memory buffer.
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*/
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size_t GetIoBufferSize() { return ioBufferSize; }
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/*
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Returns the size of the used I/O Buffer in bytes. The I/O Buffer size
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is by default set to the page size of the system.
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*/
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std::ostream& Print(std::ostream& os);
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/*
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Print the tuple buffer to stream ~os~. This function is used
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for debugging purposes.
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*/
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friend class TupleBuffer2Iterator;
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/*
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~TupleBuffer2Iterator~ is declared as friend class, so that it
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gains access to the internal and external buffers.
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*/
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private:
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const size_t MAX_MEMORY_SIZE;
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/*
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Maximum size in bytes of the internal memory buffer.
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*/
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const size_t ioBufferSize;
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/*
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I/O Buffer size for read/write operations on disk in bytes. By default
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this value is set to the page size of the operating system.
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*/
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const std::string pathName;
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/*
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Filename for the external buffer of type ~TupleFile~.
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*/
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std::queue<RTuple> memoryBuffer;
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/*
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Internal memory buffer (FIFO)
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*/
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TupleFile* diskBuffer;
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/*
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External buffer
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*/
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bool inMemory;
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/*
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Flag which is true if all tuples are kept in internal memory.
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The flag is set to false when the first tuple is moved to disk.
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*/
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static bool traceMode;
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/*
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Flag to control the trace mode. If set to true log messages
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will be produced on the standard output.
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*/
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size_t totalExtSize;
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/*
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Total size of the extension part of all tuples within the internal
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and external buffers.
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*/
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size_t totalSize;
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/*
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Total size of all tuples within the internal and external buffers.
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*/
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};
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} // end of namespace extrel2
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#endif /* TUPLEBUFFER2_H_ */
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