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com.tangosol.util.filter
Class PriorityFilter

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.net.AbstractPriorityTask
com.tangosol.util.filter.PriorityFilter

All Implemented Interfaces:

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

public class PriorityFilter

extends AbstractPriorityTask

implements IndexAwareFilter, ExternalizableLite, PortableObject

PriorityFilter is used to explicitly control the scheduling priority and timeouts for execution of filter-based methods.

For example, let's assume that there is a cache that belongs to a partitioned cache service configured with a request-timeout and task-timeout of 5 seconds. Also assume that we are willing to wait longer for a particular rarely executed parallel query that does not employ any indexes. Then we could override the default timeout values by using the PriorityFilter as follows:

   EqualsFilter   filterStandard = new LikeFilter("getComments", "%fail%");
   PriorityFilter filterPriority = new PriorityFilter(filterStandard);
   filterPriority.setExecutionTimeoutMillis(PriorityTask.TIMEOUT_NONE);
   filterPriority.setRequestTimeoutMillis(PriorityTask.TIMEOUT_NONE);
   Set setEntries = cache.entrySet(filterPriority);
 

This is an advanced feature which should be used judiciously.

Since:

Coherence 3.3

Author:

gg 2007.03.20

Field Summary

Fields inherited from interface com.tangosol.net.PriorityTask

SCHEDULE_FIRST, SCHEDULE_IMMEDIATE, SCHEDULE_STANDARD, TIMEOUT_DEFAULT, TIMEOUT_NONE

Constructor Summary

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

PriorityFilter(IndexAwareFilter filter)
Construct a PriorityFilter.

Method Summary

Filter	applyIndex(java.util.Map mapIndexes, java.util.Set setKeys) Filter remaining keys using a Map of available indexes.
int	calculateEffectiveness(java.util.Map mapIndexes, java.util.Set setKeys) Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.
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.
IndexAwareFilter	getFilter() Obtain the underlying filter.
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.net.AbstractPriorityTask

getExecutionTimeoutMillis, getRequestTimeoutMillis, getSchedulingPriority, runCanceled, setExecutionTimeoutMillis, setRequestTimeoutMillis, setSchedulingPriority

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

PriorityFilter

public PriorityFilter()

Default constructor (necessary for the ExternalizableLite interface).

PriorityFilter

public PriorityFilter(IndexAwareFilter filter)

Construct a PriorityFilter.

Parameters:

filter - the filter wrapped by this PriorityFilter

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

calculateEffectiveness

public int calculateEffectiveness(java.util.Map mapIndexes,
                                  java.util.Set setKeys)

Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.

The returned value is an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys. An operation that requires no more than a single access to the index content (i.e. Equals, NotEquals) has an effectiveness of one. Evaluation of a single entry is assumed to have an effectiveness that depends on the index implementation and is usually measured as a constant number of the single operations. This number is referred to as evaluation cost.

If the effectiveness of a filter evaluates to a number larger than the keySet.size() * <evaluation cost> then a user could avoid using the index and iterate through the keySet calling evaluate rather then applyIndex.

Specified by:

calculateEffectiveness in interface IndexAwareFilter

Parameters:

mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only

setKeys - the set of keys that will be filtered; read-only

Returns:

an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys

applyIndex

public Filter applyIndex(java.util.Map mapIndexes,
                         java.util.Set setKeys)

Filter remaining keys using a Map of available indexes.

The filter is responsible for removing all keys from the passed set of keys that the applicable indexes can prove should be filtered. If the filter does not fully evaluate the remaining keys using just the index information, it must return a filter (which may be an EntryFilter) that can complete the task using an iterating implementation. If, on the other hand, the filter does fully evaluate the remaining keys using just the index information, then it should return null to indicate that no further filtering is necessary.

Specified by:

applyIndex in interface IndexAwareFilter

Parameters:

mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only

setKeys - the mutable set of keys that remain to be filtered

Returns:

a Filter object (which may be an EntryFilter) that can be used to process the remaining keys, or null if no additional filter processing is necessary

getFilter

public IndexAwareFilter getFilter()

Obtain the underlying filter.

Returns:

the filter wrapped by this PriorityFilter

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

Overrides:

readExternal in class AbstractPriorityTask

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

Overrides:

writeExternal in class AbstractPriorityTask

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.

The AbstractPriorityTask implementation reserves property indexes 0 - 9.

This implementation reserves property index 10.

Specified by:

readExternal in interface PortableObject

Overrides:

readExternal in class AbstractPriorityTask

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.

The AbstractPriorityTask implementation reserves property indexes 0 - 9.

This implementation reserves property index 10.

Specified by:

writeExternal in interface PortableObject

Overrides:

writeExternal in class AbstractPriorityTask

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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