casacore::ColumnCache Class Reference

A caching object for a table column. More...

#include <ColumnCache.h>

Public Member Functions
	ColumnCache ()
	Constructor. More...
void	setIncrement (rownr_t increment)
	Set the increment to the given value. More...
void	set (rownr_t startRow, rownr_t endRow, const void *dataPtr)
	Set the start and end row number for which the given data pointer is valid. More...
void	invalidate ()
	Invalidate the cache. More...
Int64	offset (rownr_t rownr) const
	Calculate the offset in the cached data for the given row. More...
const void *	dataPtr () const
	Give a pointer to the data. More...
rownr_t	start () const
	Give the start, end (including), and increment row number of the cached column values. More...
rownr_t	end () const
rownr_t	incr () const

Private Attributes
rownr_t	itsStart
rownr_t	itsEnd
rownr_t	itsIncr
const void *	itsData

Detailed Description

A caching object for a table column.

Intended use:

Internal

Review Status

Reviewed By:

UNKNOWN

Date Reviewed:

before2004/08/25

Prerequisite

• ScalarColumn

Synopsis

ColumnCache acts as a cache for a table column. It contains a pointer to data and the start and end row number for which these data are valid. An increment is part of the object and is usually 0 or 1. The value 0 is used for data which is valid for multiple rows (as used in IncrementalStMan). The value 1 is used for data stored consecutevily in a buffer for each row (as used in StManAipsIO).

The ColumnCache object is created and updated by the data manager. The top level ScalarColumn object contains a pointer to the cache object. In this way the ScalarColumn::get can often be executed by a few inlined statements which improves performance considerably.

The invalidate function can be used to invalidate the cache. This is for instance needed when a table lock is acquired or released to be sure that the cache gets refreshed.

Motivation

This class was developed to improve the performance for getting a scalar.

To Do

• For ConcatColumn add the ability to have other ColumnCache objects using this one and invalidate them as well.

Definition at line 86 of file ColumnCache.h.

Constructor & Destructor Documentation

casacore::ColumnCache::ColumnCache

(

)

Constructor.

It sets the increment to 1 and calls invalidate.

Member Function Documentation

const void * casacore::ColumnCache::dataPtr ( ) const

inline

Give a pointer to the data.

The calling function has to do a proper cast after which the calculated offset can be added to get the proper data.

Definition at line 150 of file ColumnCache.h.

References itsData.

Referenced by casacore::ScalarColumn< casacore::String >::get().

rownr_t casacore::ColumnCache::end ( ) const

inline

Definition at line 117 of file ColumnCache.h.

References itsEnd.

rownr_t casacore::ColumnCache::incr ( ) const

inline

Definition at line 119 of file ColumnCache.h.

References itsIncr.

void casacore::ColumnCache::invalidate ( )

inline

Invalidate the cache.

This clears the data pointer and sets startRow>endRow.

Definition at line 135 of file ColumnCache.h.

References set().

Int64 casacore::ColumnCache::offset ( rownr_t  rownr ) const

inline

Calculate the offset in the cached data for the given row.

-1 is returned if the row is not within the cached rows.

Definition at line 140 of file ColumnCache.h.

References itsEnd, itsIncr, itsStart, and casacore::max().

Referenced by casacore::ScalarColumn< casacore::String >::get().

void casacore::ColumnCache::set	(	rownr_t	startRow,
		rownr_t	endRow,
		const void *	dataPtr
	)

Set the start and end row number for which the given data pointer is valid.

Referenced by invalidate().

void casacore::ColumnCache::setIncrement ( rownr_t  increment )

inline

Set the increment to the given value.

Definition at line 130 of file ColumnCache.h.

References itsIncr.

rownr_t casacore::ColumnCache::start ( ) const

inline

Give the start, end (including), and increment row number of the cached column values.

Definition at line 115 of file ColumnCache.h.

References itsStart.

Member Data Documentation

const void* casacore::ColumnCache::itsData

private

Definition at line 126 of file ColumnCache.h.

Referenced by dataPtr().

rownr_t casacore::ColumnCache::itsEnd

private

Definition at line 124 of file ColumnCache.h.

Referenced by end(), and offset().

rownr_t casacore::ColumnCache::itsIncr

private

Definition at line 125 of file ColumnCache.h.

Referenced by incr(), offset(), and setIncrement().

rownr_t casacore::ColumnCache::itsStart

private

Definition at line 123 of file ColumnCache.h.

Referenced by offset(), and start().

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

• tables/Tables/ColumnCache.h