org.janusgraph.diskstorage.keycolumnvalue.inmemory

Class InMemoryKeyColumnValueStore

java.lang.Object

org.janusgraph.diskstorage.keycolumnvalue.inmemory.InMemoryKeyColumnValueStore

All Implemented Interfaces:

KeyColumnValueStore

public class InMemoryKeyColumnValueStore
extends Object
implements KeyColumnValueStore

An in-memory implementation of KeyColumnValueStore. This implementation is thread-safe. All data is held in memory, which means that the capacity of this store is determined by the available heap space. No data is persisted and all data lost when the jvm terminates or store closed.

Author:

Matthias Broecheler (me@matthiasb.com)

Field Summary

Fields inherited from interface org.janusgraph.diskstorage.keycolumnvalue.KeyColumnValueStore

NO_ADDITIONS, NO_DELETIONS

Constructor Summary

Constructors

Constructor and Description
InMemoryKeyColumnValueStore(String name)

Method Summary

Modifier and Type	Method and Description
void	acquireLock(StaticBuffer key, StaticBuffer column, StaticBuffer expectedValue, StoreTransaction txh) Attempts to claim a lock on the value at the specified key and column pair.
void	clear()
void	close() Closes this store
KeyIterator	getKeys(KeyRangeQuery query, StoreTransaction txh) Returns a KeyIterator over all keys that fall within the key-range specified by the given query and have one or more columns matching the column-range.
KeyIterator	getKeys(SliceQuery query, StoreTransaction txh) Returns a KeyIterator over all keys in the store that have one or more columns matching the column-range.
String	getName() Returns the name of this store.
EntryList	getSlice(KeySliceQuery query, StoreTransaction txh) Retrieves the list of entries (i.e.
Map<StaticBuffer,EntryList>	getSlice(List<StaticBuffer> keys, SliceQuery query, StoreTransaction txh) Retrieves the list of entries (i.e.
void	mutate(StaticBuffer key, List<Entry> additions, List<StaticBuffer> deletions, StoreTransaction txh) Verifies acquisition of locks txh from previous calls to KeyColumnValueStore.acquireLock(StaticBuffer, StaticBuffer, StaticBuffer, StoreTransaction) , then writes supplied additions and/or deletions to key in the underlying data store.

Methods inherited from class java.lang.Object

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

Constructor Detail

InMemoryKeyColumnValueStore

public InMemoryKeyColumnValueStore(String name)

Method Detail

getSlice

public EntryList getSlice(KeySliceQuery query,
                          StoreTransaction txh)
                   throws BackendException

Description copied from interface: KeyColumnValueStore

Retrieves the list of entries (i.e. column-value pairs) for a specified query.

Specified by:

getSlice in interface KeyColumnValueStore

Parameters:

query - Query to get results for

txh - Transaction

Returns:

List of entries up to a maximum of "limit" entries

Throws:

BackendException - when columnEnd < columnStart

See Also:

KeySliceQuery

getSlice

public Map<StaticBuffer,EntryList> getSlice(List<StaticBuffer> keys,
                                            SliceQuery query,
                                            StoreTransaction txh)
                                     throws BackendException

Description copied from interface: KeyColumnValueStore

Retrieves the list of entries (i.e. column-value pairs) as specified by the given SliceQuery for all of the given keys together.

Specified by:

getSlice in interface KeyColumnValueStore

Parameters:

keys - List of keys

query - Slicequery specifying matching entries

txh - Transaction

Returns:

The result of the query for each of the given keys as a map from the key to the list of result entries.

Throws:

BackendException

mutate

public void mutate(StaticBuffer key,
                   List<Entry> additions,
                   List<StaticBuffer> deletions,
                   StoreTransaction txh)
            throws BackendException

Description copied from interface: KeyColumnValueStore

Verifies acquisition of locks txh from previous calls to KeyColumnValueStore.acquireLock(StaticBuffer, StaticBuffer, StaticBuffer, StoreTransaction) , then writes supplied additions and/or deletions to key in the underlying data store. Deletions are applied strictly before additions. In other words, if both an addition and deletion are supplied for the same column, then the column will first be deleted and then the supplied Entry for the column will be added.

Implementations which don't support locking should skip the initial lock verification step but otherwise behave as described above.

Specified by:

mutate in interface KeyColumnValueStore

Parameters:

key - the key under which the columns in additions and deletions will be written

additions - the list of Entry instances representing column-value pairs to create under key, or null to add no column-value pairs

deletions - the list of columns to delete from key, or null to delete no columns

txh - the transaction to use

Throws:

PermanentLockingException - if locking is supported by the implementation and at least one lock acquisition attempted by KeyColumnValueStore.acquireLock(StaticBuffer, StaticBuffer, StaticBuffer, StoreTransaction) has failed

BackendException

acquireLock

public void acquireLock(StaticBuffer key,
                        StaticBuffer column,
                        StaticBuffer expectedValue,
                        StoreTransaction txh)
                 throws BackendException

Description copied from interface: KeyColumnValueStore

Attempts to claim a lock on the value at the specified key and column pair. These locks are discretionary.

If locking fails, implementations of this method may, but are not required to, throw PermanentLockingException. This method is not required to determine whether locking actually succeeded and may return without throwing an exception even when the lock can't be acquired. Lock acquisition is only only guaranteed to be verified by the first call to KeyColumnValueStore.mutate(StaticBuffer, List, List, StoreTransaction) on any given txh.

The expectedValue must match the actual value present at the key and column pair. If the true value does not match the expectedValue, the lock attempt fails and LockingException is thrown. This method may check expectedValue. The mutate() mutate is required to check it.

When this method is called multiple times on the same key, column, and txh, calls after the first have no effect.

Locks acquired by this method must be automatically released on transaction commit() or rollback().

Implementations which don't support locking should throw UnsupportedOperationException.

Specified by:

acquireLock in interface KeyColumnValueStore

Parameters:

key - the key on which to lock

column - the column on which to lock

expectedValue - the expected value for the specified key-column pair on which to lock (null means the pair must have no value)

txh - the transaction to use

Throws:

PermanentLockingException - the lock could not be acquired due to contention with other transactions or a locking-specific storage problem

BackendException

getKeys

public KeyIterator getKeys(KeyRangeQuery query,
                           StoreTransaction txh)
                    throws BackendException

Description copied from interface: KeyColumnValueStore

Returns a KeyIterator over all keys that fall within the key-range specified by the given query and have one or more columns matching the column-range. Calling KeyIterator.getEntries() returns the list of all entries that match the column-range specified by the given query.

This method is only supported by stores which keep keys in byte-order.

Specified by:

getKeys in interface KeyColumnValueStore

Returns:

Throws:

BackendException

getKeys

public KeyIterator getKeys(SliceQuery query,
                           StoreTransaction txh)
                    throws BackendException

Description copied from interface: KeyColumnValueStore

Returns a KeyIterator over all keys in the store that have one or more columns matching the column-range. Calling KeyIterator.getEntries() returns the list of all entries that match the column-range specified by the given query.

This method is only supported by stores which do not keep keys in byte-order.

Specified by:

getKeys in interface KeyColumnValueStore

Returns:

Throws:

BackendException

getName

public String getName()

Description copied from interface: KeyColumnValueStore

Returns the name of this store. Each store has a unique name which is used to open it.

Specified by:

getName in interface KeyColumnValueStore

Returns:

store name

See Also:

KeyColumnValueStoreManager.openDatabase(String)

clear

public void clear()

close

public void close()
           throws BackendException

Description copied from interface: KeyColumnValueStore

Closes this store

Specified by:

close in interface KeyColumnValueStore

Throws:

BackendException