casa::SSMIndex Class Reference [Tables_module_internal_classes]

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

#include <SSMIndex.h>

List of all members.

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

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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.

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Constructor & Destructor Documentation

casa::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.

casa::SSMIndex::~SSMIndex

(

)

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Member Function Documentation

void casa::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 casa::SSMIndex::addRow

(

uInt

aNrRows

)

Add some rows.

Int casa::SSMIndex::deleteRow

(

uInt

aRowNumber

)

Delete the given row.

void casa::SSMIndex::find	(	uInt	aRowNumber,
		uInt &	aBucketNr,
		uInt &	aStartRow,
		uInt &	anEndRow
	)			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 casa::SSMIndex::get

(

AipsIO &

anOs

)

Read the bucket index from the AipsIO object.

Vector<uInt> casa::SSMIndex::getBuckets

(

)

const

Return all the bucketnrs used in this index.

Int casa::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 casa::SSMIndex::getIndex

(

uInt

aRowNr

)

const [private]

Get the index of the bucket containing the given row.

uInt casa::SSMIndex::getNrBuckets

(

)

const

Return the nr of buckets used.

uInt casa::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 casa::SSMIndex::put

(

AipsIO &

anOs

)

const

Write the bucket index into the AipsIO object.

void casa::SSMIndex::recreate

(

)

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

Int casa::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 casa::SSMIndex::setNrColumns	(	Int	aNrColumns,
		uInt	aSizeUsed
	)

Set nr of columns use this index.

void casa::SSMIndex::showStatistics

(

ostream &

anOs

)

const

Show Statistics of index.

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Member Data Documentation

Block<uInt> casa::SSMIndex::itsBucketNumber [private]

Definition at line 163 of file SSMIndex.h.

SimpleOrderedMap<Int,Int> casa::SSMIndex::itsFreeSpace [private]

Definition at line 166 of file SSMIndex.h.

Block<uInt> casa::SSMIndex::itsLastRow [private]

Definition at line 158 of file SSMIndex.h.

Int casa::SSMIndex::itsNrColumns [private]

Definition at line 172 of file SSMIndex.h.

uInt casa::SSMIndex::itsNUsed [private]

Definition at line 155 of file SSMIndex.h.

uInt casa::SSMIndex::itsRowsPerBucket [private]

Definition at line 169 of file SSMIndex.h.

Referenced by getRowsPerBucket().

SSMBase* casa::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:

• tables/Tables/SSMIndex.h