Give access to some StandardStMan functions. More...

#include <StandardStManAccessor.h>

Inheritance diagram for casa::ROStandardStManAccessor:

Public Member Functions
	ROStandardStManAccessor (const Table &table, const String &name, Bool byColumn=False)
	Construct the object for a data manager in the table given the name of the data manager or the column.
virtual	~ROStandardStManAccessor ()
	ROStandardStManAccessor (const ROStandardStManAccessor &that)
	Copy constructor (reference semantics).
ROStandardStManAccessor &	operator= (const ROStandardStManAccessor &that)
	Assignment (reference semantics).
void	setCacheSize (uInt aSize, Bool canExceedNrBuckets=True)
	Set the cache size (in buckets) to be used by the storage manager.
uInt	getCacheSize () const
	Get the cache size (in buckets).
void	clearCache ()
	Clear the cache used by this storage manager.
void	showBaseStatistics (ostream &anOs) const
	Show the statistics for the base class.
void	showIndexStatistics (ostream &anOs) const
	Show the statistics for each index used by this storage manager.
Private Attributes
SSMBase *	itsSSMPtr

Detailed Description

Give access to some StandardStMan functions.

Intended use:

Public interface

Review Status

Reviewed By:: UNKNOWN
Date Reviewed:: before2004/08/25
Test programs:: tStandardStMan

Prerequisite

StandardStMan

Synopsis

The Table system has one or more storage managers underneath. One of these possible storage managers is the StandardStMan . This storage manager uses a cache of buckets. The default cache size is defined when the StandardStMan object was constructed at the time the table was created.

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 ROStandardStManAccessor makes it possible to change the cache size in a temporary way.
It is also possible to get the cache size.

Furthermore it is possible to show some statistics (about the cache and the internals of SSM classes).

Motivation

In principle a pointer to StandardStMan could be used. However, that would give access to all public functions. Furthermore it could not distinguish between read/write and readonly tables.

Example

This example shows how to set the cache size for the standard storage manager with the name "SSMExample". The cache size is not persistent, i.e. when the same table is reopened at a later time, this cache size is not remembered.

     // Open a table.
     Table table("someName.data");
     // Set the cache size of its standard storage manager SSMExample
     // to 5 buckets.
     ROStandardStManAccessor accessor(table, "SSMExample");
     accessor.setCacheSize (5);

Definition at line 103 of file StandardStManAccessor.h.

Constructor & Destructor Documentation

casa::ROStandardStManAccessor::ROStandardStManAccessor	(	const Table &	table,
		const String &	name,
		Bool	byColumn = `False`
	)

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.

virtual casa::ROStandardStManAccessor::~ROStandardStManAccessor ( ) [virtual]

casa::ROStandardStManAccessor::ROStandardStManAccessor ( const ROStandardStManAccessor & that )

Copy constructor (reference semantics).

Member Function Documentation

void casa::ROStandardStManAccessor::clearCache ( )

Clear the cache used by this storage manager.

It will flush the cache as needed and remove all buckets from it resulting in a drop in memory used.

uInt casa::ROStandardStManAccessor::getCacheSize ( ) const

Get the cache size (in buckets).

ROStandardStManAccessor& casa::ROStandardStManAccessor::operator= ( const ROStandardStManAccessor & that )

Assignment (reference semantics).

void casa::ROStandardStManAccessor::setCacheSize	(	uInt	aSize,
		Bool	canExceedNrBuckets = `True`
	)

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 Standard storage managers, is persistent. If canExceedNrBuckets=True, 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 casa::ROStandardStManAccessor::showBaseStatistics ( ostream & anOs ) const

Show the statistics for the base class.

void casa::ROStandardStManAccessor::showIndexStatistics ( ostream & anOs ) const

Show the statistics for each index used by this storage manager.

Member Data Documentation

SSMBase* casa::ROStandardStManAccessor::itsSSMPtr [private]

Definition at line 152 of file StandardStManAccessor.h.

The documentation for this class was generated from the following file:

casacore/tables/Tables/StandardStManAccessor.h

Public Member Functions

Private Attributes