uk.org.ogsadai.client.databrowser.sql
Class DBJoin

java.lang.Object
  |
  +--uk.org.ogsadai.client.databrowser.sql.DBJoin

public class DBJoin

extends java.lang.Object

Handles a "Join" across databases.

Version:

$Revision: 1.13 $

Author:

Paul J Graham, EPCC

Field Summary

private static java.lang.String	COPYRIGHT_NOTICE Copyright statement
private static DataTransportMode	MODE The mode of the data transfer, here we use BLOCK
private static TimeoutProperty	TEN_MINUTE_TIMEOUT timeout property for a 10 minute timeout
private static int	TEN_MINUTES timeout of the request

Constructor Summary

DBJoin()

Method Summary

private void	createTable(DataService service, DBUpdate createTable)
private void	destroyTable(DataService service, DBUpdate dropTable) Destroy a table
private java.lang.String	getTableName(DBUpdate update) Gets the intermediate table name (assumes the SQL statement ends with the table name, e.g.
java.sql.ResultSet	join(DBProgressModel pm, DBJoinParameter params) Performs a join.
private DTOutputStream	launchOutputActivity(SQLQuery query, WebRowSet webrowset, DataService service, Session session) Launches an output activity which sends the results of a query to an output stream for use in another activity.
private void	performBulkLoad(DTOutputStream outputStream, java.lang.String tableNameTo, DataService serviceFrom, DataService serviceTo) Delivers data from a source data service resource and bulk loads this data into a table at the sink data service resource.

Methods inherited from class java.lang.Object

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

Field Detail

COPYRIGHT_NOTICE

private static final java.lang.String COPYRIGHT_NOTICE

Copyright statement

See Also:

Constant Field Values

MODE

private static final DataTransportMode MODE

The mode of the data transfer, here we use BLOCK

TEN_MINUTES

private static final int TEN_MINUTES

timeout of the request

See Also:

Constant Field Values

TEN_MINUTE_TIMEOUT

private static final TimeoutProperty TEN_MINUTE_TIMEOUT

timeout property for a 10 minute timeout

Constructor Detail

DBJoin

public DBJoin()

Method Detail

join

public java.sql.ResultSet join(DBProgressModel pm,
                               DBJoinParameter params)
                        throws java.lang.Exception

Performs a join. Runs a join across three databases. First two temporary tables are created in database C. Then databases A and B are queried and the results delivered (via BulkLoad) to the temporary tables. Then the join query is run across the temp tables, the result of this join returned and the temporary tables destroyed. If an error occurs during execution of any of the above steps an attempt will be made to drop the temporary tables.

Parameters:

pm - The progress monitor

params - The join parameters

Returns:

The result of the join

Throws:

java.lang.Exception - if anything goes wrong while executing actions on the services.

getTableName

private java.lang.String getTableName(DBUpdate update)

Gets the intermediate table name (assumes the SQL statement ends with the table name, e.g. 'DROP TABLE tablename')

Parameters:

update - The 'DROP TABLE' SQL

Returns:

The name of the temporary table

destroyTable

private void destroyTable(DataService service,
                          DBUpdate dropTable)
                   throws java.lang.Exception

Destroy a table

Parameters:

service - The service which will run the SQL

dropTable - The SQL to run 'DROP TABLE ...'

Throws:

java.lang.Exception - if anything goes wrong while executing the action on the service.

createTable

private void createTable(DataService service,
                         DBUpdate createTable)
                  throws java.lang.Exception

Parameters:

service - The data service which will run the SQL

createTable - The SQL to run 'CREATE TABLE ...'

Throws:

java.lang.Exception - if anything goes wrong while executing the action on the service.

launchOutputActivity

private DTOutputStream launchOutputActivity(SQLQuery query,
                                            WebRowSet webrowset,
                                            DataService service,
                                            Session session)
                                     throws java.lang.Exception

Launches an output activity which sends the results of a query to an output stream for use in another activity.

Parameters:

query - The SQL query activity

webrowset - The webrowset result convertor activity which contains the output

service - The data service to run the query

Returns:

The name of the output stream (required for input to another activity

Throws:

java.lang.Exception - if anything goes wrong while executing the action on the service.

performBulkLoad

private void performBulkLoad(DTOutputStream outputStream,
                             java.lang.String tableNameTo,
                             DataService serviceFrom,
                             DataService serviceTo)
                      throws java.lang.Exception

Delivers data from a source data service resource and bulk loads this data into a table at the sink data service resource.

Parameters:

outputStream - The name of the output activity

tableNameTo - The name of the table where the results will be loaded

serviceFrom - The source data service providing data via an output stream

serviceTo - The sink data service performing the loading activity

Throws:

java.lang.Exception - if anything goes wrong while executing the action on the service.