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

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

DBJoin

public DBJoin()

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.