uk.ac.starlink.ttools.cone

Class ParallelResultRowSequence

java.lang.Object

uk.ac.starlink.ttools.cone.ParallelResultRowSequence

All Implemented Interfaces:

Closeable, AutoCloseable, RowData, RowSequence, ConeQueryRowSequence, ConeResultRowSequence, Sequence

public class ParallelResultRowSequence
extends Object
implements ConeResultRowSequence

ConeResultRowSequence implementation which uses a fixed number of worker threads to dispatch cone queries in parallel. The result table has the same ordering as if they had been done in sequence.

Since:

18 Jan 2008

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_MAXPAR Default maximum value for the number of threads that should be permitted for a query.
static String	MAXPAR_PROP Name of system property "service.maxparallel" which may be used to adjust the maximum parallelism.

Constructor Summary

Constructors

Constructor and Description
ParallelResultRowSequence(ConeQueryRowSequence querySeq, ConeSearcher coneSearcher, ConeErrorPolicy errAct, Coverage coverage, boolean bestOnly, boolean distFilter, String distanceCol, int parallelism) Constructor.

Method Summary

Modifier and Type	Method and Description
void	close() Indicates that this sequence will not be required any more.
Object	getCell(int icol) Returns the contents of a cell in the current row.
StarTable	getConeResult() Returns the result of the cone search for the current row of this sequence.
double	getDec() Get central declination for the current row's cone search request in degrees.
long	getIndex() Get the index in the underlying table to which the current row relates.
static int	getMaxParallelism() Returns the maximum parallelism value which should permitted in this JVM.
double	getRa() Get central right ascension for the current row's cone search request in degrees.
double	getRadius() Get search radius for the current row's cone search request in degrees.
Object[]	getRow() Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table.
boolean	next() Attempts to advance the current row to the next one.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAXPAR

public static final int DEFAULT_MAXPAR

Default maximum value for the number of threads that should be permitted for a query.

See Also:

MAXPAR_PROP, getMaxParallelism(), Constant Field Values

MAXPAR_PROP

public static final String MAXPAR_PROP

Name of system property "service.maxparallel" which may be used to adjust the maximum parallelism. Only increase this value with great care since you run the risk of overloading servers and making yourself unpopular with data centres. As a rule, you should only increase this value if you have obtained permission from the data centres whose services on which you will be using the increased parallelism.

See Also:

DEFAULT_MAXPAR, getMaxParallelism(), Constant Field Values

Constructor Detail

ParallelResultRowSequence

public ParallelResultRowSequence(ConeQueryRowSequence querySeq,
                                 ConeSearcher coneSearcher,
                                 ConeErrorPolicy errAct,
                                 Coverage coverage,
                                 boolean bestOnly,
                                 boolean distFilter,
                                 String distanceCol,
                                 int parallelism)

Constructor.

Parameters:

querySeq - sequence providing cone search query parameters

coneSearcher - cone search implementation

errAct - defines action on cone search invocation error

coverage - coverage for results, or null

bestOnly - whether all results or just best are required

distFilter - true to perform post-query filtering on results based on the distance between the query position and the result row position

distanceCol - name of column to hold distance information in output table, or null

parallelism - number of concurrent querying threads

Method Detail

next

public boolean next()
             throws IOException

Description copied from interface: RowSequence

Attempts to advance the current row to the next one. If true is returned the attempt has been successful, and if false is returned there are no more rows in this sequence. Since the initial position of a RowSequence is before the first row, this method must be called before current row data can be accessed using the RowSequence.getCell(int) or RowSequence.getRow() methods.

Specified by:

next in interface RowSequence

Specified by:

next in interface Sequence

Returns:

true iff this sequence has been advanced to the next row

Throws:

IOException - if there is some error

getCell

public Object getCell(int icol)
               throws IOException

Description copied from interface: RowSequence

Returns the contents of a cell in the current row. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass(). An unchecked exception will be thrown if there is no current row (next has not yet been called).

Specified by:

getCell in interface RowData

Specified by:

getCell in interface RowSequence

Parameters:

icol - column index

Returns:

the contents of cell icol in the current row

Throws:

IOException - if there is an error reading the data

getRow

public Object[] getRow()
                throws IOException

Description copied from interface: RowSequence

Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table. An unchecked exception will be thrown if there is no current row (next has not yet been called).

Specified by:

getRow in interface RowData

Specified by:

getRow in interface RowSequence

Returns:

an array of the objects in each cell in row irow

Throws:

IOException - if there is an error reading the data

getRa

public double getRa()
             throws IOException

Description copied from interface: ConeQueryRowSequence

Get central right ascension for the current row's cone search request in degrees.

Specified by:

getRa in interface ConeQueryRowSequence

Returns:

right ascension

Throws:

IOException

getDec

public double getDec()
              throws IOException

Description copied from interface: ConeQueryRowSequence

Get central declination for the current row's cone search request in degrees.

Specified by:

getDec in interface ConeQueryRowSequence

Returns:

declination

Throws:

IOException

getRadius

public double getRadius()
                 throws IOException

Description copied from interface: ConeQueryRowSequence

Get search radius for the current row's cone search request in degrees.

Specified by:

getRadius in interface ConeQueryRowSequence

Returns:

search radius

Throws:

IOException

getIndex

public long getIndex()
              throws IOException

Description copied from interface: ConeQueryRowSequence

Get the index in the underlying table to which the current row relates. The identity of this underlying table is not specified by this interface, but must be understood by the creator and user of instances. In particular, the return value does not necessarily increment by one for each call to next.

Specified by:

getIndex in interface ConeQueryRowSequence

Returns:

row index

Throws:

IOException

getConeResult

public StarTable getConeResult()
                        throws IOException

Description copied from interface: ConeResultRowSequence

Returns the result of the cone search for the current row of this sequence. The work will typically be done using ConeMatcher.getConeResult(uk.ac.starlink.ttools.cone.ConeSearcher, uk.ac.starlink.ttools.cone.ConeErrorPolicy, boolean, boolean, java.lang.String, double, double, double).

If no records in the cone are found, the return value may either be null or (preferably) an empty table with the correct columns.

Specified by:

getConeResult in interface ConeResultRowSequence

Returns:

table giving rows strictly within the match criteria for the current row of this cone query sequence, or null

Throws:

IOException

close

public void close()
           throws IOException

Description copied from interface: RowSequence

Indicates that this sequence will not be required any more. This should release resources associated with this object. The effect of calling any of the other methods following a close is undefined.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface RowSequence

Throws:

IOException

getMaxParallelism

public static int getMaxParallelism()

Returns the maximum parallelism value which should permitted in this JVM. The purpose of this is to set a limit to the number of concurrent queries that an irresponsible/careless user can hit a server with. The value can be adjusted using the MAXPAR_PROP system property. Note that this method is not used by this class, i.e. the maximum is not imposed here, it should be imposed by calling code.

Returns:

parallelism limit