uk.ac.starlink.ttools.filter

Class JELSelectorTable

java.lang.Object

uk.ac.starlink.table.WrapperStarTable

uk.ac.starlink.ttools.filter.JELSelectorTable

All Implemented Interfaces:

Closeable, AutoCloseable, StarTable

public class JELSelectorTable
extends WrapperStarTable

Sequential table which selects rows on the basis of a JEL-interpreted expression.

See Also:

JELRowReader

Field Summary

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

baseTable

Constructor Summary

Constructors

Constructor and Description
JELSelectorTable(StarTable baseTable, String expr) Construct a table given a base table and a selection expression.

Method Summary

Modifier and Type	Method and Description
Object	getCell(long irow, int icol) Returns the contents of a given table cell.
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.
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() Indicates whether random access is provided by this table.

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

JELSelectorTable

public JELSelectorTable(StarTable baseTable,
                        String expr)
                 throws gnu.jel.CompilationException

Construct a table given a base table and a selection expression.

Parameters:

baseTable - base table

expr - boolean algebraic expression describing inclusion test

Throws:

gnu.jel.CompilationException

Method Detail

isRandom

public boolean isRandom()

Description copied from interface: StarTable

Indicates whether random access is provided by this table. Only if the result is true may the StarTable.getRowAccess(), StarTable.getRow(long) and StarTable.getCell(long, int) methods be used.

Specified by:

isRandom in interface StarTable

Overrides:

isRandom in class WrapperStarTable

Returns:

true if table random access methods are available

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

getCell

public Object getCell(long irow,
                      int icol)

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

getRow

public Object[] getRow(long irow)

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

getRowAccess

public RowAccess getRowAccess()

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

getRowSequence

public RowSequence getRowSequence()
                           throws 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:

IOException - if there is an error providing access

getRowSplittable

public RowSplittable getRowSplittable()
                               throws 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:

IOException

See Also:

RowRunner