net.fortytwo.stream.caching

Class SolutionIndex<T>

java.lang.Object

net.fortytwo.stream.caching.SolutionIndex<T>

public class SolutionIndex<T>
extends java.lang.Object

An index of partial and complete solutions for a particular query

Author:

Joshua Shinavier (http://fortytwo.net)

Constructor Summary

Constructors

Constructor and Description
SolutionIndex(Query.QueryVariables queryVariables, int totalPatterns) Constructs a new solution index

Method Summary

Modifier and Type	Method and Description
boolean	add(Solution<T> s, long now) Adds a solution to this index.
java.util.Iterator<Solution<T>>	composeSolutions(java.lang.String variable, T value, Solution<T> ps, long now)
java.util.Iterator<Solution<T>>	getComposableSolutions(java.lang.String variable, T value, Solution<T> ps, long now)
java.util.Iterator<Solution<T>>	getSolutions(java.lang.String variable, T value, long now) Retrieves all unexpired solutions for a given variable/value pair
void	joinSolutions(Solution<T> matchedSolution, Bindings<T> bindings, java.util.Stack<Solution<T>> solutions, long now) Finds the result of joining composable combinations of an original solution together with all unexpired solutions containing any of a provided set of bindings.
int	removeExpired(long now) Removes all expired solutions from this index.

Methods inherited from class java.lang.Object

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

Constructor Detail

SolutionIndex

public SolutionIndex(Query.QueryVariables queryVariables,
                     int totalPatterns)

Constructs a new solution index

Parameters:

queryVariables - the variables of the query for which this is an index

totalPatterns - the total number of tuple patterns in the query for which this is an index

Method Detail

add

public boolean add(Solution<T> s,
                   long now)

Adds a solution to this index.

Parameters:

s - the solution to add

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

Returns:

whether the solution was actually added, rather than being ignored due to equality with or containment within another solution which does not expire sooner

getSolutions

public java.util.Iterator<Solution<T>> getSolutions(java.lang.String variable,
                                                    T value,
                                                    long now)

Retrieves all unexpired solutions for a given variable/value pair

Parameters:

variable - a query variable

value - a value bound to a query variable

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

Returns:

an iterator over all solutions to the query which contain the given binding

getComposableSolutions

public java.util.Iterator<Solution<T>> getComposableSolutions(java.lang.String variable,
                                                              T value,
                                                              Solution<T> ps,
                                                              long now)

composeSolutions

public java.util.Iterator<Solution<T>> composeSolutions(java.lang.String variable,
                                                        T value,
                                                        Solution<T> ps,
                                                        long now)

joinSolutions

public void joinSolutions(Solution<T> matchedSolution,
                          Bindings<T> bindings,
                          java.util.Stack<Solution<T>> solutions,
                          long now)

Finds the result of joining composable combinations of an original solution together with all unexpired solutions containing any of a provided set of bindings.

Parameters:

matchedSolution - the initial solution produced by matching the tuple pattern against the tuple

bindings - a set of bindings

solutions - a stack of solutions which will be cleared, and to which solutions will be added

now - the current clock time

removeExpired

public int removeExpired(long now)

Removes all expired solutions from this index. This is an exhaustive, top-down operation which takes a relatively large amount of time.

Parameters:

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

Returns:

the number of solutions removed