net.fortytwo.stream.caching

Class Query<T,S>

java.lang.Object

net.fortytwo.stream.caching.Query<T,S>

All Implemented Interfaces:

java.lang.Comparable<Query<T,S>>

public class Query<T,S>
extends java.lang.Object
implements java.lang.Comparable<Query<T,S>>

A graph query composed of a set of tuple patterns. Each query also has a unique ID and a finite or infinite expiration time. A query must be submitted to at most one query index, which sets the ID in addition to other fields used in query answering. Furthermore, a query should not be submitted more than once to a query index, although it may be renewed with QueryIndex.renew().

Author:

Joshua Shinavier (http://fortytwo.net)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Query.PatternInQuery<T,C> A tuple pattern with a reference to the containing query, as well as its index within that query
static class	Query.QueryVariables An array of variables used in a query, mapping an integer index to variable names and vice versa

Constructor Summary

Constructors

Constructor and Description
Query(java.util.List<VariableOrConstant<java.lang.String,T>[]> patterns, long expirationTime) Constructs a new query given a set of tuple patterns and an expiration time

Method Summary

Modifier and Type	Method and Description
int	compareTo(Query<T,S> other) Orders queries by increasing expiration time
java.util.List<Query.PatternInQuery<T,S>>	getPatterns() Gets this query's tuple patterns
SolutionIndex<T>	getSolutionIndex() Gets the solution index stored along with this query
S	getSubscription() Get the unique ID of the query
Query.QueryVariables	getVariables() Gets this query's variables
boolean	isExpired(long now) Gets the expiration status of this query
void	setExpirationTime(long expirationTime) Sets a new expiration time for this query.
void	setSubscription(S subscription) Sets the subscription of the query.

Methods inherited from class java.lang.Object

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

Constructor Detail

Query

public Query(java.util.List<VariableOrConstant<java.lang.String,T>[]> patterns,
             long expirationTime)

Constructs a new query given a set of tuple patterns and an expiration time

Parameters:

patterns - the graph pattern, or set of tuple patterns, which defines this query

expirationTime - the time, in milliseconds, since the Unix epoch at which this query will automatically become inactve and be removed from the index. If the special value 0 is supplied as the expiration time, the query will never expire, but may be removed explicitly.

Method Detail

getSubscription

public S getSubscription()

Get the unique ID of the query

Returns:

the unique ID of the query. This is assigned automatically by the query index

setSubscription

public void setSubscription(S subscription)

Sets the subscription of the query. If this query is managed by a query index, it should not be necessary to set this elsewhere.

Parameters:

subscription - the subscription

getPatterns

public java.util.List<Query.PatternInQuery<T,S>> getPatterns()

Gets this query's tuple patterns

Returns:

this query's graph pattern, or list of tuple patterns

getVariables

public Query.QueryVariables getVariables()

Gets this query's variables

Returns:

the set of variables which appear in the tuple patterns of this query

getSolutionIndex

public SolutionIndex<T> getSolutionIndex()

Gets the solution index stored along with this query

Returns:

the solution index stored along with this query, used by the query index As there can be only one solution index, a query may only be submitted to one query index.

isExpired

public boolean isExpired(long now)

Gets the expiration status of this query

Parameters:

now - the current time, in milliseconds since the Unix epoch

Returns:

whether this query has expired. An expired query will produce no additional answers, and is automatically removed from the query index.

setExpirationTime

public void setExpirationTime(long expirationTime)

Sets a new expiration time for this query. This method should not be called once the query has been submitted to an index, which manages its expiration from that point on.

Parameters:

expirationTime - the new expiration time of this query, in milliseconds since the Unix epoch. A special value of 0 indicates that the query should never expire.

compareTo

public int compareTo(Query<T,S> other)

Orders queries by increasing expiration time

Specified by:

compareTo in interface java.lang.Comparable<Query<T,S>>