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com.tangosol.util.filter
Class PartitionedFilter

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.util.filter.PartitionedFilter

All Implemented Interfaces:

ExternalizableLite, PortableObject, Filter, EntryFilter, java.io.Serializable

public class PartitionedFilter

extends ExternalizableHelper

implements EntryFilter, ExternalizableLite, PortableObject

Filter which limits the scope of another filter to those entries that have keys that belong to the specified partition set.

This filter is intended to be used in advanced scenarios, when a caller wants to retrieve the results of parallel processing restricted to a subset of partitions. This approach may somewhat complicate the client code, but can dramatically reduce the memory footprint used by the requestor.

Below are two examples of PartitionedFilter usage:

• Run a parallel query partition-by-partition:

   void executeByPartitions(NamedCache cache, Filter filter)
       {
       DistributedCacheService service =
           (DistributedCacheService) cache.getCacheService();
       int cPartitions = service.getPartitionCount();
  
       PartitionSet parts = new PartitionSet(cPartitions);
       for (int iPartition = 0; iPartition < cPartitions; iPartition++)
           {
           parts.add(iPartition);
  
           Filter filterPart = new PartitionedFilter(filter, parts);
  
           Set setEntriesPart = cache.entrySet(filterPart);
  
           // process the entries ...
  
           parts.remove(iPartition);
           }
       }
  

• Run a parallel query member-by-member:

   void executeByMembers(NamedCache cache, Filter f)
       {
       DistributedCacheService service =
           (DistributedCacheService) cache.getCacheService();
       int cPartitions = service.getPartitionCount();
  
       PartitionSet partsProcessed = new PartitionSet(cPartitions);
       for (Iterator iter = service.getStorageEnabledMembers().iterator();
               iter.hasNext();)
           {
           Member member = (Member) iter.next();
  
           PartitionSet partsMember = service.getOwnedPartitions(member);
  
           // due to a redistribution some partitions may have already been processed
           partsMember.remove(partsProcessed);
  
           Filter filterPart = new PartitionedFilter(filter, partsMember);
           Set setEntriesPart = cache.entrySet(filterPart);
  
           // process the entries ...
  
           partsProcessed.add(partsMember);
           }
  
       // due to a possible redistribution, some partitions may have been skipped
       if (!partsProcessed.isFull())
           {
           partsProcessed.invert();
           Filter filter = new PartitionedFilter(filter, partsProcessed);
  
           // process the remaining entries ...
           }
       }
  

Note: This filter must be the outermost filter and cannot be used as a part of any composite filter (AndFilter, OrFilter, etc.)

To iterate through a query on a partition-by-partition or member-by-member basis, use the PartitionedIterator class.

Since:

Coherence 3.4

Author:

gg 2008.02.06

Constructor Summary

PartitionedFilter()
Default constructor (necessary for the ExternalizableLite interface).

PartitionedFilter(Filter filter, PartitionSet partitions)
Construct a PartitionedFilter.

Method Summary

boolean	equals(java.lang.Object o) Compare the PartitionedFilter with another object to determine equality.
boolean	evaluate(java.lang.Object o) Apply the test to the object.
boolean	evaluateEntry(java.util.Map.Entry entry) Apply the test to a Map Entry.
Filter	getFilter() Obtain the wrapped Filter.
PartitionSet	getPartitionSet() Obtain the PartitionSet that specifies what partitions the wrapped filter will be applied to.
int	hashCode() Determine a hash value for the PartitionedFilter object according to the general Object.hashCode() contract.
void	readExternal(java.io.DataInput in) Restore the contents of this object by loading the object's state from the passed DataInput object.
void	readExternal(PofReader in) Restore the contents of a user type instance by reading its state using the specified PofReader object.
java.lang.String	toString() Return a human-readable description for this Filter.
void	writeExternal(java.io.DataOutput out) Save the contents of this object by storing the object's state into the passed DataOutput object.
void	writeExternal(PofWriter out) Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Methods inherited from class com.tangosol.util.BitHelper

countBits, countBits, countBits, indexOfLSB, indexOfLSB, indexOfLSB, indexOfMSB, indexOfMSB, indexOfMSB, rotateLeft, rotateLeft, rotateLeft, rotateRight, rotateRight, rotateRight, toBitString, toBitString, toBitString

Constructor Detail

PartitionedFilter

public PartitionedFilter()

Default constructor (necessary for the ExternalizableLite interface).

PartitionedFilter

public PartitionedFilter(Filter filter,
                         PartitionSet partitions)

Construct a PartitionedFilter.

Parameters:

filter - the underlying (wrapped) filter

partitions - the subset of partitions the filter should run against

Method Detail

evaluate

public boolean evaluate(java.lang.Object o)

Apply the test to the object.

Specified by:

evaluate in interface Filter

Parameters:

o - the object to test

Returns:

true if the test passes, false otherwise

evaluateEntry

public boolean evaluateEntry(java.util.Map.Entry entry)

Apply the test to a Map Entry.

Specified by:

evaluateEntry in interface EntryFilter

Parameters:

entry - the Map Entry to evaluate; never null

Returns:

true if the test passes, false otherwise

getFilter

public Filter getFilter()

Obtain the wrapped Filter.

Returns:

the wrapped filter object

getPartitionSet

public PartitionSet getPartitionSet()

Obtain the PartitionSet that specifies what partitions the wrapped filter will be applied to.

Returns:

the partition set

equals

public boolean equals(java.lang.Object o)

Compare the PartitionedFilter with another object to determine equality. Two PartitionedFilter objects are considered equal iff the wrapped filters and partition sets are equal.

Returns:

true iff this PartitionedFilter and the passed object are equivalent PartitionedFilter objects

hashCode

public int hashCode()

Determine a hash value for the PartitionedFilter object according to the general Object.hashCode() contract.

Returns:

an integer hash value for this PartitionedFilter object

toString

public java.lang.String toString()

Return a human-readable description for this Filter.

Returns:

a String description of the Filter

readExternal

public void readExternal(java.io.DataInput in)
                  throws java.io.IOException

Restore the contents of this object by loading the object's state from the passed DataInput object.

Specified by:

readExternal in interface ExternalizableLite

Parameters:

in - the DataInput stream to read data from in order to restore the state of this object

Throws:

java.io.IOException - if an I/O exception occurs

java.io.NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

writeExternal

public void writeExternal(java.io.DataOutput out)
                   throws java.io.IOException

Save the contents of this object by storing the object's state into the passed DataOutput object.

Specified by:

writeExternal in interface ExternalizableLite

Parameters:

out - the DataOutput stream to write the state of this object to

Throws:

java.io.IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws java.io.IOException

Restore the contents of a user type instance by reading its state using the specified PofReader object.

Specified by:

readExternal in interface PortableObject

Parameters:

in - the PofReader from which to read the object's state

Throws:

java.io.IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws java.io.IOException

Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Specified by:

writeExternal in interface PortableObject

Parameters:

out - the PofWriter to which to write the object's state

Throws:

java.io.IOException - if an I/O error occurs

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