org.gridgain.grid.kernal.processors.cache.query.jdbc

Class GridCacheQueryJdbcMetadataTask

java.lang.Object

org.gridgain.grid.compute.GridComputeTaskAdapter<String,byte[]>

org.gridgain.grid.kernal.processors.cache.query.jdbc.GridCacheQueryJdbcMetadataTask

All Implemented Interfaces:

Serializable, GridComputeTask<String,byte[]>

public class GridCacheQueryJdbcMetadataTask
extends GridComputeTaskAdapter<String,byte[]>

Task that gets metadata for JDBC adapter.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
GridCacheQueryJdbcMetadataTask()

Method Summary

Methods

Modifier and Type	Method and Description
Map<? extends GridComputeJob,GridNode>	map(List<GridNode> subgrid, String cacheName) This method is called to map or split grid task into multiple grid jobs.
byte[]	reduce(List<GridComputeJobResult> results) Reduces (or aggregates) results received so far into one compound result to be returned to caller via GridComputeTaskFuture.get() method.

Methods inherited from class org.gridgain.grid.compute.GridComputeTaskAdapter

result

Methods inherited from class java.lang.Object

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

Constructor Detail

GridCacheQueryJdbcMetadataTask

public GridCacheQueryJdbcMetadataTask()

Method Detail

map

public Map<? extends GridComputeJob,GridNode> map(List<GridNode> subgrid,
                                         @Nullable
                                         String cacheName)
                                           throws GridException

This method is called to map or split grid task into multiple grid jobs. This is the first method that gets called when task execution starts.

Parameters:

subgrid - Nodes available for this task execution. Note that order of nodes is guaranteed to be randomized by container. This ensures that every time you simply iterate through grid nodes, the order of nodes will be random which over time should result into all nodes being used equally.

cacheName - Task execution argument. Can be null. This is the same argument as the one passed into Grid#execute(...) methods.

Returns:

Map of grid jobs assigned to subgrid node. Unless GridComputeTaskContinuousMapper is injected into task, if null or empty map is returned, exception will be thrown.

Throws:

GridException - If mapping could not complete successfully. This exception will be thrown out of GridComputeTaskFuture.get() method.

reduce

public byte[] reduce(List<GridComputeJobResult> results)
              throws GridException

Reduces (or aggregates) results received so far into one compound result to be returned to caller via GridComputeTaskFuture.get() method.

Note, that if some jobs did not succeed and could not be failed over then the list of results passed into this method will include the failed results. Otherwise, failed results will not be in the list.

Parameters:

results - Received results of broadcasted remote executions. Note that if task class has GridComputeTaskNoResultCache annotation, then this list will be empty.

Returns:

Grid job result constructed from results of remote executions.

Throws:

GridException - If reduction or results caused an error. This exception will be thrown out of GridComputeTaskFuture.get() method.