IncrStManAccessor.h

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// # IncrStManAccessor.h: Gives access to some IncrementalStMan functions
// # Copyright (C) 1996,1999,2000,2001
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef TABLES_INCRSTMANACCESSOR_H
#define TABLES_INCRSTMANACCESSOR_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/tables/DataMan/DataManAccessor.h>
#include <casacore/casa/iosfwd.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward Declarations
class ISMBase;
class DataManager;
class Table;
class String;
 
// <summary>
// Give access to some IncrementalStMan functions
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="" demos="">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
// <li> <linkto class=IncrementalStMan>IncrementalStMan</linkto>
// </prerequisite>
 
// <synopsis>
// The Table system has one or more storage managers underneath.
// One of these possible storage managers is the
// <linkto class=IncrementalStMan>IncrementalStMan</linkto>.
// This storage manager uses a cache of buckets. The default
// cache size is defined when the IncrementalStMan object was
// constructed at the time the table was created.
// <p>
// Sometimes it can be useful to change the cache size. E.g. when
// the table is accessed in a random way, the hit rate may drop
// when the cache is too small. The class ROIncrStManAccessor makes
// it possible to change the cache size in a temporary way.
// <br>
// Furthermore this class makes it possible to show the cache size
// and to show the cache statistics.
 
// <motivation>
// In principle a pointer to IncrementalStMan could be used.
// However, that would give access to all public functions.
// Furthermore it could not distinguish between read/write and readonly
// tables.
// </motivation>
 
// <example>
// This example shows how to set the cache size for
// the incremental storage manager with the name "ISMExample". The cache
// size is not persistent, i.e. when the same table is reopened
// at a later time, this cache size is not remembered.
// <srcblock>
//  // Open a table.
//  Table table("someName.data");
//  // Set the cache size of its incremental storage manager ISMExample
//  // to 5 buckets.
//  ROIncrementalStManAccessor accessor(table, "ISMExample");
//  accessor.setCacheSize (5);
// </srcblock>
// </example>
 
// # <todo asof="$DATE:$">
// # </todo>
 
class ROIncrementalStManAccessor : public RODataManAccessor {
 public:
  // Construct the object for a data manager in the table given the name
  // of the data manager or the column.
  // An exception is thrown if the data manager type is not the incremental
  // storage manager.
  ROIncrementalStManAccessor(const Table& table, const String& name, Bool byColumn = False);
 
  virtual ~ROIncrementalStManAccessor();
 
  // Copy constructor (reference semantics).
  ROIncrementalStManAccessor(const ROIncrementalStManAccessor& that);
 
  // Assignment (reference semantics).
  ROIncrementalStManAccessor& operator=(const ROIncrementalStManAccessor& that);
 
  // Set the cache size (in buckets) to be used by the
  // storage manager.
  // The cache size given in this way is not persistent.
  // Only the cache size given to the constructors of the incremental
  // storage managers, is persistent.
  // If <src>canExceedNrBuckets=True</src>, the given cache size can be
  // larger than the nr of buckets in the file. In this way the cache can
  // be made large enough for a future file extnsion.
  // Otherwise, it is limited to the actual number of buckets. This is useful
  // if one wants the entire file to be cached.
  void setCacheSize(uInt aSize, Bool canExceedNrBuckets = True);
 
  // Get the cache size (in buckets).
  uInt cacheSize() const;
 
  // Clear the caches used by the hypercubes in this storage manager.
  // It will flush the caches as needed and remove all buckets from them
  // resulting in a possibly large drop in memory used.
  void clearCache();
 
  // Show the index used by this storage manager.
  void showIndexStatistics(ostream& os) const;
 
  // Show the layout of the buckets used by this storage manager.
  void showBucketLayout(ostream& os) const;
 
  // Check that there are no repeated rowIds in the buckets comprising this ISM
  Bool checkBucketLayout(uInt& offendingCursor, rownr_t& offendingBucketStartRow,
                         uInt& offendingBucketNrow, uInt& offendingBucketNr, uInt& offendingCol,
                         uInt& offendingIndex, rownr_t& offendingRow,
                         rownr_t& offendingPrevRow) const;
 
 private:
  // # Declare the data members.
  ISMBase* dataManPtr_p;
};
 
}  // namespace casacore
 
#endif