org.janusgraph.graphdb.transaction.subquerycache

Class SubsetSubqueryCache

java.lang.Object

org.janusgraph.graphdb.transaction.subquerycache.SubsetSubqueryCache

All Implemented Interfaces:

SubqueryCache

Direct Known Subclasses:

CaffeineSubqueryCache

public abstract class SubsetSubqueryCache
extends Object
implements SubqueryCache

Different from a simple exact mapping from keys to values, it leverages the fact that the results of a Subquery A with limit X are first X entries of the results of the a Subquery B with limit Y, where A and B only differ in limit, and X is less than or equal to Y.

For example, suppose the cache is empty at the beginning. Firstly, prop1_idx:multiKSQ[1]@100 query leads to a cache miss, and then results are loaded into cache. Secondly, prop1_idx:multiKSQ[1]@20 query leads to a cache hit, and then first 20 results of cached responses are returned. Thirdly, prop1_idx:multiKSQ[1]@2000 leads to a cache miss, then results are loaded into cache, and initial results saved by prop1_idx:multiKSQ[1]@100 query are overriden by the new results.

Internally, raw query results are encapsulated in SubqueryResult object together with limit of the query. Meanwhile, keys are stored without limit (or with a dummy limit). Whenever there is a hit for key, the limit of cached results and that of the query will be compared, and whether this is a cache hit or miss will be determined.

Compared to a simply JointIndexQuery.Subquery to List<Object> mapping, this cache has two benefits: 1) it reduces latency, as "subset" queries can effectively leverage cached results. 2) it saves space, as queries only differing in limit will not be saved more than once in cache.

Author:

Boxuan Li ([email protected])

Constructor Summary

Constructors

Constructor and Description
SubsetSubqueryCache()

Method Summary

Modifier and Type	Method and Description
protected abstract org.janusgraph.graphdb.transaction.subquerycache.SubsetSubqueryCache.SubqueryResult	get(JointIndexQuery.Subquery key)
List<Object>	get(JointIndexQuery.Subquery key, Callable<? extends List<Object>> valueLoader) Returns a list of results.
List<Object>	getIfPresent(JointIndexQuery.Subquery key) Return a list of results if given query exists in cache, otherwise return null
void	put(JointIndexQuery.Subquery key, List<Object> values) Add given values into cache
protected abstract void	put(JointIndexQuery.Subquery key, org.janusgraph.graphdb.transaction.subquerycache.SubsetSubqueryCache.SubqueryResult result)

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.janusgraph.graphdb.transaction.subquerycache.SubqueryCache

close

Constructor Detail

SubsetSubqueryCache

public SubsetSubqueryCache()

Method Detail

get

protected abstract org.janusgraph.graphdb.transaction.subquerycache.SubsetSubqueryCache.SubqueryResult get(JointIndexQuery.Subquery key)

put

protected abstract void put(JointIndexQuery.Subquery key,
                            org.janusgraph.graphdb.transaction.subquerycache.SubsetSubqueryCache.SubqueryResult result)

getIfPresent

public List<Object> getIfPresent(JointIndexQuery.Subquery key)

Description copied from interface: SubqueryCache

Return a list of results if given query exists in cache, otherwise return null

Specified by:

getIfPresent in interface SubqueryCache

Parameters:

key - a subquery of joint index query

Returns:

a list of matching results or null if is not in the cache

put

public void put(JointIndexQuery.Subquery key,
                List<Object> values)

Description copied from interface: SubqueryCache

Add given values into cache

Specified by:

put in interface SubqueryCache

Parameters:

key - a subquery of joint index query

values - a list of results to be cached

get

public List<Object> get(JointIndexQuery.Subquery key,
                        Callable<? extends List<Object>> valueLoader)
                 throws Exception

Description copied from interface: SubqueryCache

Returns a list of results. If given query not in cache, call the value loader to retrieve results and put into the cache

Specified by:

get in interface SubqueryCache

Parameters:

key - a subquery of joint index query

valueLoader - a callable that returns a list of results

Returns:

a list of results

Throws:

Exception - if exception thrown when calling the value loader