io.permazen.kv.util

Class ForwardingKVStore

java.lang.Object

io.permazen.kv.util.ForwardingKVStore

All Implemented Interfaces:

KVStore

Direct Known Subclasses:

CloseableForwardingKVStore, FallbackKVTransaction, LevelDBAtomicKVStore, LMDBKVTransaction, PrefixKVStore, RocksDBAtomicKVStore, SnapshotKVTransaction, SpannerKVTransaction, SQLKVTransaction, UnmodifiableKVStore, XodusKVTransaction

public abstract class ForwardingKVStore
extends Object
implements KVStore

Forwards all KVStore operations to another underlying KVStore.

Constructor Summary

Constructors

Constructor and Description
ForwardingKVStore()

Method Summary

Modifier and Type	Method and Description
void	adjustCounter(byte[] key, long amount) Adjust the counter at the given key by the given amount.
void	apply(Mutations mutations) Apply all the given Mutations to this instance.
long	decodeCounter(byte[] bytes) Decode a counter value previously encoded by encodeCounter().
protected abstract KVStore	delegate() Get the underlying KVStore.
byte[]	encodeCounter(long value) Encode a counter value into a byte[] value suitable for use with decodeCounter() and/or adjustCounter().
byte[]	get(byte[] key) Get the value associated with the given key, if any.
KVPair	getAtLeast(byte[] minKey, byte[] maxKey) Get the key/value pair having the smallest key greater than or equal to the given minimum, if any.
KVPair	getAtMost(byte[] maxKey, byte[] minKey) Get the key/value pair having the largest key strictly less than the given maximum, if any.
CloseableIterator<KVPair>	getRange(byte[] minKey, byte[] maxKey, boolean reverse) Iterate the key/value pairs in the specified range.
void	put(byte[] key, byte[] value) Set the value associated with the given key.
void	remove(byte[] key) Remove the key/value pair with the given key, if it exists.
void	removeRange(byte[] minKey, byte[] maxKey) Remove all key/value pairs whose keys are in a given range.

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.permazen.kv.KVStore

getRange, getRange, removeRange

Constructor Detail

ForwardingKVStore

public ForwardingKVStore()

Method Detail

delegate

protected abstract KVStore delegate()

Get the underlying KVStore.

Returns:

underlying KVStore

get

public byte[] get(byte[] key)

Description copied from interface: KVStore

Get the value associated with the given key, if any.

Modifications to the returned byte[] array do not affect this instance.

Specified by:

get in interface KVStore

Parameters:

key - key

Returns:

value associated with key, or null if not found

getAtLeast

public KVPair getAtLeast(byte[] minKey,
                         byte[] maxKey)

Description copied from interface: KVStore

Get the key/value pair having the smallest key greater than or equal to the given minimum, if any.

An optional (exclusive) maximum key may also be specified; if maxKey is null, there is no upper bound; if maxKey <= minKey, null is always returned.

If keys starting with 0xff are not supported by this instance, and minKey starts with 0xff, then this method returns null.

Modifications to the returned byte[] arrays do not affect this instance.

Specified by:

getAtLeast in interface KVStore

Parameters:

minKey - minimum key (inclusive), or null for no minimum (get the smallest key)

maxKey - maximum key (exclusive), or null for no maximum (no upper bound)

Returns:

smallest key/value pair with key >= minKey and key < maxKey, or null if none exists

getAtMost

public KVPair getAtMost(byte[] maxKey,
                        byte[] minKey)

Description copied from interface: KVStore

Get the key/value pair having the largest key strictly less than the given maximum, if any.

An optional (inclusive) minimum key may also be specified; if minKey is null, there is no lower bound (equivalent to a lower bound of the empty byte array); if minKey >= maxKey, null is always returned.

If keys starting with 0xff are not supported by this instance, and maxKey starts with 0xff, then this method behaves as if maxKey were null.

Modifications to the returned byte[] arrays do not affect this instance.

Specified by:

getAtMost in interface KVStore

Parameters:

maxKey - maximum key (exclusive), or null for no maximum (get the largest key)

minKey - minimum key (inclusive), or null for no minimum (no lower bound)

Returns:

largest key/value pair with key < maxKey and key >= minKey, or null if none exists

getRange

public CloseableIterator<KVPair> getRange(byte[] minKey,
                                          byte[] maxKey,
                                          boolean reverse)

Description copied from interface: KVStore

Iterate the key/value pairs in the specified range. The returned Iterator's remove() method must be supported and should have the same effect as invoking remove() on the corresponding key.

If keys starting with 0xff are not supported by this instance, and minKey starts with 0xff, then this method returns an empty iteration.

If keys starting with 0xff are not supported by this instance, and maxKey starts with 0xff, then this method behaves as if maxKey were null.

The returned Iterator must not throw ConcurrentModificationException; however, whether or not a "live" Iterator reflects any modifications made after its creation is implementation dependent. Implementations that do make post-creation updates visible in the Iterator, even if the update occurs after some delay, must preserve the order in which the modifications actually occurred.

The returned Iterator itself is not guaranteed to be thread safe.

Invokers of this method are encouraged to close() the returned iterators, though this is not required for correct behavior.

Modifications to the returned KVPair key and value byte[] arrays do not affect this instance.

Specified by:

getRange in interface KVStore

Parameters:

minKey - minimum key (inclusive), or null for no minimum (start at the smallest key)

maxKey - maximum key (exclusive), or null for no maximum (end at the largest key)

reverse - true to return key/value pairs in reverse order (i.e., keys descending)

Returns:

iteration of key/value pairs in the range minKey (inclusive) to maxKey (exclusive)

put

public void put(byte[] key,
                byte[] value)

Description copied from interface: KVStore

Set the value associated with the given key.

Specified by:

put in interface KVStore

Parameters:

key - key

value - value

remove

public void remove(byte[] key)

Description copied from interface: KVStore

Remove the key/value pair with the given key, if it exists.

Specified by:

remove in interface KVStore

Parameters:

key - key

removeRange

public void removeRange(byte[] minKey,
                        byte[] maxKey)

Description copied from interface: KVStore

Remove all key/value pairs whose keys are in a given range.

The minKey must be less than or equal to maxKey; if they equal (and not null) then nothing happens; if they are both null then all entries are deleted.

If keys starting with 0xff are not supported by this instance, then:

• If minKey starts with 0xff, then no change occurs
• If maxKey starts with 0xff, then this method behaves as if maxKey were null

Specified by:

removeRange in interface KVStore

Parameters:

minKey - minimum key (inclusive), or null for no minimum

maxKey - maximum key (exclusive), or null for no maximum

adjustCounter

public void adjustCounter(byte[] key,
                          long amount)

Description copied from interface: KVStore

Adjust the counter at the given key by the given amount.

Ideally this operation should behave in a lock-free manner, so that concurrent transactions can invoke it without conflict. However, when lock-free behavior occurs (if at all) depends on the implementation.

If there is no value associated with key, or key's value is not a valid counter encoding as would be acceptable to decodeCounter(), then how this operation affects key's value is undefined.

Specified by:

adjustCounter in interface KVStore

Parameters:

key - key

amount - amount to adjust counter value by

encodeCounter

public byte[] encodeCounter(long value)

Description copied from interface: KVStore

Encode a counter value into a byte[] value suitable for use with decodeCounter() and/or adjustCounter().

Specified by:

encodeCounter in interface KVStore

Parameters:

value - desired counter value

Returns:

encoded counter value

decodeCounter

public long decodeCounter(byte[] bytes)

Description copied from interface: KVStore

Decode a counter value previously encoded by encodeCounter().

Specified by:

decodeCounter in interface KVStore

Parameters:

bytes - encoded counter value

Returns:

decoded counter value

apply

public void apply(Mutations mutations)

Description copied from interface: KVStore

Apply all the given Mutations to this instance.

Mutations are always to be applied in this order: removes, puts, counter adjustments.

The implementation in KVStore simply iterates over the individual changes and applies them via remove() (for removals of a single key), removeRange(), put(), and/or adjustCounter(). Implementations that can process batch updates more efficiently are encouraged to override this method.

Specified by:

apply in interface KVStore

Parameters:

mutations - mutations to apply