uk.ac.starlink.table

Class RowPermutedStarTable

java.lang.Object

uk.ac.starlink.table.WrapperStarTable

uk.ac.starlink.table.RowPermutedStarTable

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, StarTable

public class RowPermutedStarTable
extends WrapperStarTable

Wrapper table which provides a view of a base table in which the rows are permuted. Each row in the wrapper table is a view of one in the base table. It is permitted for the wrapper to contain multiple views of the same column in the base.

A long[] array, rowMap, is used to keep track of which rows in this table correspond to which rows in the base table; the n'th row in this table corresponds to the rowMap[n]'th row in the base table. The rowMap array may contain duplicate entries, but should not contain any entries larger than the number of rows in the base table. Any negative entry is treated as a special case resulting in a 'blank' row of all null values. It can be modified during the life of the table, but it's not a good idea to do this while a RowSequence is active.

Field Summary

Fields inherited from class uk.ac.starlink.table.WrapperStarTable

baseTable

Constructor Summary

Constructors

Constructor and Description
RowPermutedStarTable(StarTable baseTable) Constructs a new RowPermutedTable with rows initially in unpermuted order.
RowPermutedStarTable(StarTable baseTable, long[] rowMap) Constructs a new RowPermutedStarTable from a base table and a rowMap array.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	getCell(long irow, int icol) Returns the contents of a given table cell.
java.lang.Object[]	getRow(long irow) Returns the contents of a given table row.
RowAccess	getRowAccess() Returns an object which can provide random access to this table's data, if random access is implemented.
long	getRowCount() Returns the number of rows in this table, if known.
long[]	getRowMap() Returns the mapping array.
RowSequence	getRowSequence() Returns an object which can iterate over all the rows in the table sequentially.
RowSplittable	getRowSplittable() Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.
boolean	isRandom() Returns true.
void	setRowMap(long[] rowMap) Sets the mapping array.

Methods inherited from class uk.ac.starlink.table.WrapperStarTable

checkedLongToInt, close, getBaseTable, getColumnAuxDataInfos, getColumnCount, getColumnInfo, getName, getParameterByName, getParameters, getURL, setName, setParameter, setURL, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

RowPermutedStarTable

public RowPermutedStarTable(StarTable baseTable,
                            long[] rowMap)

Constructs a new RowPermutedStarTable from a base table and a rowMap array.

baseTable must provide random access.

Parameters:

baseTable - base table

rowMap - array mapping rows in the new permuted table to rows in baseTable

Throws:

java.lang.IllegalArgumentException - if baseTable.isRandom returns false

RowPermutedStarTable

public RowPermutedStarTable(StarTable baseTable)

Constructs a new RowPermutedTable with rows initially in unpermuted order.

Parameters:

baseTable - base table

Method Detail

getRowMap

public long[] getRowMap()

Returns the mapping array.

Returns:

array mapping rows in this table to rows in the base table

setRowMap

public void setRowMap(long[] rowMap)

Sets the mapping array.

Parameters:

rowMap - array mapping rows in this table to rows in the base table

getRowCount

public long getRowCount()

Description copied from interface: StarTable

Returns the number of rows in this table, if known. If the number of rows cannot be (easily) determined, a value of -1 will be returned.

Specified by:

getRowCount in interface StarTable

Overrides:

getRowCount in class WrapperStarTable

Returns:

the number of rows, or -1

isRandom

public boolean isRandom()

Returns true.

Specified by:

isRandom in interface StarTable

Overrides:

isRandom in class WrapperStarTable

Returns:

true if table random access methods are available

getRowAccess

public RowAccess getRowAccess()
                       throws java.io.IOException

Description copied from interface: StarTable

Returns an object which can provide random access to this table's data, if random access is implemented. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowAccess in interface StarTable

Overrides:

getRowAccess in class WrapperStarTable

Returns:

new RowAccess

Throws:

java.io.IOException - if there is an error setting up access

getRowSequence

public RowSequence getRowSequence()
                           throws java.io.IOException

Description copied from interface: StarTable

Returns an object which can iterate over all the rows in the table sequentially. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowSequence in interface StarTable

Overrides:

getRowSequence in class WrapperStarTable

Returns:

new RowSequence

Throws:

java.io.IOException - if there is an error providing access

getRowSplittable

public RowSplittable getRowSplittable()
                               throws java.io.IOException

Description copied from interface: StarTable

Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.

The return value must be non-null, and may provide splitting arrangements specially appropriate for the implementation. If this table 'wraps' an upstream table, it is usually best to base the implementation on calls to the the upstream getRowSplittable method, so that upstream policy about how to divide up the table is respected. However, implementations without special requirements may return Tables.getDefaultRowSplittable(this).

Specified by:

getRowSplittable in interface StarTable

Overrides:

getRowSplittable in class WrapperStarTable

Returns:

new RowSplittable

Throws:

java.io.IOException

See Also:

RowRunner

getCell

public java.lang.Object getCell(long irow,
                                int icol)
                         throws java.io.IOException

Description copied from interface: StarTable

Returns the contents of a given table cell. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass().

This method is safe for concurrent use from multiple threads, but in general it is recommended to use a RowAccess instead.

Specified by:

getCell in interface StarTable

Overrides:

getCell in class WrapperStarTable

Parameters:

irow - the index of the cell's row

icol - the index of the cell's column

Returns:

the contents of this cell

Throws:

java.io.IOException - if there is an error reading the data

getRow

public java.lang.Object[] getRow(long irow)
                          throws java.io.IOException

Description copied from interface: StarTable

Returns the contents of a given table row. The returned value is equivalent to an array formed of all the objects returned by getCell(irow,icol) for all the columns icol in sequence.

This method is safe for concurrent use from multiple threads, but in general it is recommended to use a RowAccess instead.

Specified by:

getRow in interface StarTable

Overrides:

getRow in class WrapperStarTable

Parameters:

irow - the index of the row to retrieve

Returns:

an array of the objects in each cell in row irow

Throws:

java.io.IOException - if there is an error reading the data