casacore::SSMIndex Class Reference

The bucket index for a group of columns in the Standard Storage Manager. More...

#include <SSMIndex.h>

Public Member Functions
	SSMIndex (SSMBase *aPtrSSM, uInt rowsPerBucket=0)
	Create the object with the given number of rows per bucket. More...
	~SSMIndex ()
void	get (AipsIO &anOs)
	Read the bucket index from the AipsIO object. More...
void	put (AipsIO &anOs) const
	Write the bucket index into the AipsIO object. More...
void	recreate ()
	Recreate the object in case all rows are deleted from the table. More...
Vector< uInt >	getBuckets () const
	Return all the bucketnrs used in this index. More...
uInt	getNrBuckets () const
	Return the nr of buckets used. More...
void	setNrColumns (Int aNrColumns, uInt aSizeUsed)
	Set nr of columns use this index. More...
void	addRow (uInt aNrRows)
	Add some rows. More...
void	showStatistics (ostream &anOs) const
	Show Statistics of index. More...
Int	removeColumn (Int anOffset, uInt nbits)
	A column is removed. More...
Int	getFree (Int &anOffset, uInt nbits) const
	Try to find free space for a field with a given length (best fit). More...
void	addColumn (Int anOffset, uInt nbits)
	reuse the space at offset for a field with the given nr of bits. More...
Int	deleteRow (uInt aRowNumber)
	Delete the given row. More...
uInt	getRowsPerBucket () const
	Get the number of rows that fits in ach bucket. More...
void	find (uInt aRowNumber, uInt &aBucketNr, uInt &aStartRow, uInt &anEndRow, const String &colName) const
	Find the bucket containing the given row. More...

Private Member Functions
uInt	getIndex (uInt aRowNr, const String &colName) const
	Get the index of the bucket containing the given row. More...

Private Attributes
SSMBase *	itsSSMPtr
uInt	itsNUsed
Block< uInt >	itsLastRow
Block< uInt >	itsBucketNumber
std::map< Int, Int >	itsFreeSpace
uInt	itsRowsPerBucket
Int	itsNrColumns

Detailed Description

The bucket index for a group of columns in the Standard Storage Manager.

Intended use:

Internal

Review Status

Reviewed By:

UNKNOWN

Date Reviewed:

before2004/08/25

Test programs:

tStandardStMan

Prerequisite

• SSMBase

Etymology

SSMIndex represent the bucket index in the Standard Storage Manager.

Synopsis

In SSMBase it is described that an index is used to map row number to data bucket in a bucket stream. This class implements this index. It serves 2 purposes:

1. It keeps a block of row numbers giving the last row number stored in each data bucket.
   Note that each bucket does not need to contain the same number of rows, because rows might be deleted from it. When all rows are deleted from a bucket, the bucket is removed from the index and added to the free bucket list.
2. When a column is deleted, the bucket will have a hole. SSMIndex maintains a map to know the size and offset of each hole. Adjacent holes are combined. When a new column is added SSMBase will scan the SSMIndex objects to find the hole fitting best.

To Do

• recreate should recreate the itsLastRow && itsBucketNr as well (moving them to the front and rearrange the freespace as one concatenated block)

Definition at line 86 of file SSMIndex.h.

Constructor & Destructor Documentation

casacore::SSMIndex::SSMIndex ( SSMBase *  aPtrSSM, uInt  rowsPerBucket = 0  )

explicit

Create the object with the given number of rows per bucket.

Note that the default is needed to create the object for existing tables.

casacore::SSMIndex::~SSMIndex

(

)

Member Function Documentation

void casacore::SSMIndex::addColumn	(	Int	anOffset,
		uInt	nbits
	)

reuse the space at offset for a field with the given nr of bits.

This is used when column has been added to this bucket.

void casacore::SSMIndex::addRow

(

uInt

aNrRows

)

Add some rows.

Int casacore::SSMIndex::deleteRow

(

uInt

aRowNumber

)

Delete the given row.

void casacore::SSMIndex::find	(	uInt	aRowNumber,
		uInt &	aBucketNr,
		uInt &	aStartRow,
		uInt &	anEndRow,
		const String &	colName
	)		const

Find the bucket containing the given row.

An exception is thrown if not found. It also sets the first and last row number fitting in that bucket.

void casacore::SSMIndex::get

(

AipsIO &

anOs

)

Read the bucket index from the AipsIO object.

Vector<uInt> casacore::SSMIndex::getBuckets

(

)

const

Return all the bucketnrs used in this index.

Int casacore::SSMIndex::getFree	(	Int &	anOffset,
		uInt	nbits
	)		const

Try to find free space for a field with a given length (best fit).

-1 is returned if no fit is found. Otherwise it returns the nr of bytes left unused.

uInt casacore::SSMIndex::getIndex ( uInt  aRowNr, const String &  colName  ) const

private

Get the index of the bucket containing the given row.

uInt casacore::SSMIndex::getNrBuckets

(

)

const

Return the nr of buckets used.

uInt casacore::SSMIndex::getRowsPerBucket ( ) const

inline

Get the number of rows that fits in ach bucket.

Definition at line 176 of file SSMIndex.h.

References itsRowsPerBucket.

void casacore::SSMIndex::put

(

AipsIO &

anOs

)

const

Write the bucket index into the AipsIO object.

void casacore::SSMIndex::recreate

(

)

Recreate the object in case all rows are deleted from the table.

Int casacore::SSMIndex::removeColumn	(	Int	anOffset,
		uInt	nbits
	)

A column is removed.

Set the free space at offset for a field with the given nr of bits. It returns the nr of columns still used in this index.

void casacore::SSMIndex::setNrColumns	(	Int	aNrColumns,
		uInt	aSizeUsed
	)

Set nr of columns use this index.

void casacore::SSMIndex::showStatistics

(

ostream &

anOs

)

const

Show Statistics of index.

Member Data Documentation

Block<uInt> casacore::SSMIndex::itsBucketNumber

private

Definition at line 163 of file SSMIndex.h.

std::map<Int,Int> casacore::SSMIndex::itsFreeSpace

private

Definition at line 166 of file SSMIndex.h.

Block<uInt> casacore::SSMIndex::itsLastRow

private

Definition at line 158 of file SSMIndex.h.

Int casacore::SSMIndex::itsNrColumns

private

Definition at line 172 of file SSMIndex.h.

uInt casacore::SSMIndex::itsNUsed

private

Definition at line 155 of file SSMIndex.h.

uInt casacore::SSMIndex::itsRowsPerBucket

private

Definition at line 169 of file SSMIndex.h.

Referenced by getRowsPerBucket().

SSMBase* casacore::SSMIndex::itsSSMPtr

private

Definition at line 152 of file SSMIndex.h.

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

• casa/casacore/tables/DataMan/SSMIndex.h