com.bigdata.btree

Class Checkpoint

java.lang.Object

com.bigdata.btree.Checkpoint

All Implemented Interfaces:

ICheckpoint, Externalizable, Serializable

Direct Known Subclasses:

MetadataIndex.MetadataIndexCheckpoint

public class Checkpoint
extends Object
implements ICheckpoint, Externalizable

A checkpoint record is written each time the btree is flushed to the store.

Note: In order to create a btree use BTree.create(IRawStore, IndexMetadata) to write the initial IndexMetadata record and the initial check point on the store. It will then load the BTree from the Checkpoint record and you can start using the index.

Author:

Bryan Thompson

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
Checkpoint() De-serialization ctor.
Checkpoint(BTree btree) Creates a Checkpoint record from a BTree.
Checkpoint(HTree htree) Creates a Checkpoint record from an HTree.
Checkpoint(IndexMetadata metadata) Create the first checkpoint record for a new BTree from a IndexMetadata record.
Checkpoint(IndexMetadata metadata, Checkpoint oldCheckpoint) Create the first checkpoint record for an existing BTree when it is propagated on overflow onto a new backing IRawStore.
Checkpoint(Stream stream) Creates a Checkpoint record from an HTree.

Method Summary

Methods

Modifier and Type	Method and Description
static ICheckpointProtocol	create(IRawStore store, IndexMetadata metadata) Generic method to create a persistence capable data structure (GIST compatible, core implementation).
long	getBloomFilterAddr() Address of the IBloomFilter.
long	getCheckpointAddr() The address used to read this Checkpoint record from the store.
long	getCounter() Return the value of the B+Tree local counter stored in the Checkpoint record.
long	getEntryCount() The #of index entries (aka tuple count).
int	getGlobalDepth() The global depth of the root directory (HTree only).
int	getHeight() The height of a B+Tree.
IndexTypeEnum	getIndexType() The type of index for this checkpoint record.
long	getLeafCount() The #of leaves (B+Tree), hash buckets (HTree), or ZERO (0) for a solution set stream.
long	getMetadataAddr() Address that can be used to read the IndexMetadata record for the index from the store.
long	getNodeCount() The #of non-leaf nodes (B+Tree) or directories (HTree).
long	getRecordVersion() Return the value of the next record version number to be assigned that is stored in the Checkpoint record.
long	getRootAddr() Address of the root node or leaf of the BTree.
boolean	hasCheckpointAddr() Return true iff the checkpoint address is defined.
static Checkpoint	load(IRawStore store, long addrCheckpoint) Read a Checkpoint record from a store.
static ICheckpointProtocol	loadFromCheckpoint(IRawStore store, long checkpointAddr, boolean readOnly) Utility method reads the Checkpoint record and then loads and returns a view of the associated read-only persistence capable data structure.
void	readExternal(ObjectInput in)
String	toString() A human readable representation of the state of the Checkpoint record.
void	write(IRawStore store) Write the Checkpoint record on the store, setting addrCheckpoint as a side effect.
void	writeExternal(ObjectOutput out)

Methods inherited from class java.lang.Object

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

Constructor Detail

Checkpoint

public Checkpoint()

De-serialization ctor.

Checkpoint

public Checkpoint(IndexMetadata metadata)

Create the first checkpoint record for a new BTree from a IndexMetadata record. The root of the BTree will NOT exist (its address will be 0L). Once written on the store the Checkpoint record may be used to obtain a corresponding instance of a BTree object.

Parameters:

metadata - The index metadata record.

Checkpoint

public Checkpoint(IndexMetadata metadata,
          Checkpoint oldCheckpoint)

Create the first checkpoint record for an existing BTree when it is propagated on overflow onto a new backing IRawStore. The counter is propagated to the new Checkpoint but otherwise the initialization is as if for an empty BTree.

Parameters:

metadata - The index metadata record.

oldCheckpoint - The last Checkpoint for the index on the old backing store. The counter is propagated to the new Checkpoint record.

Checkpoint

public Checkpoint(BTree btree)

Creates a Checkpoint record from a BTree.

Pre-conditions:

• The root is clean.
• The metadata record is clean.
• The optional bloom filter is clean if it is defined.

Note: if the root is null then the root is assumed to be clean and the root address from the last Checkpoint record is used. Otherwise the address of the root is used (in which case it MUST be defined).

Note: This method is invoked by reflection.

Parameters:

btree - The btree.

Checkpoint

public Checkpoint(HTree htree)

Creates a Checkpoint record from an HTree.

Pre-conditions:

• The root is clean.
• The metadata record is clean.
• The optional bloom filter is clean if it is defined.

Note: if the root is null then the root is assumed to be clean and the root address from the last Checkpoint record is used. Otherwise the address of the root is used (in which case it MUST be defined).

Note: This method is invoked by reflection.

Parameters:

htree - The HTree.

Checkpoint

public Checkpoint(Stream stream)

Creates a Checkpoint record from an HTree.

Pre-conditions:

• The root is clean.
• The metadata record is clean.
• The optional bloom filter is clean if it is defined.

Note: if the root is null then the root is assumed to be clean and the root address from the last Checkpoint record is used. Otherwise the address of the root is used (in which case it MUST be defined).

Note: This method is invoked by reflection.

Parameters:

stream - The HTree.

Method Detail

getCheckpointAddr

public final long getCheckpointAddr()

Description copied from interface: ICheckpoint

The address used to read this Checkpoint record from the store.

Note: This is set as a side-effect by #write(IRawStore).

Specified by:

getCheckpointAddr in interface ICheckpoint

hasCheckpointAddr

public final boolean hasCheckpointAddr()

Description copied from interface: ICheckpoint

Return true iff the checkpoint address is defined.

Specified by:

hasCheckpointAddr in interface ICheckpoint

getMetadataAddr

public final long getMetadataAddr()

Description copied from interface: ICheckpoint

Address that can be used to read the IndexMetadata record for the index from the store.

Specified by:

getMetadataAddr in interface ICheckpoint

getRootAddr

public final long getRootAddr()

Description copied from interface: ICheckpoint

Address of the root node or leaf of the BTree.

Specified by:

getRootAddr in interface ICheckpoint

Returns:

The address of the root -or- 0L iff the index does not have a root page.

getBloomFilterAddr

public final long getBloomFilterAddr()

Description copied from interface: ICheckpoint

Address of the IBloomFilter.

Specified by:

getBloomFilterAddr in interface ICheckpoint

Returns:

The address of the bloom filter -or- 0L iff the index does not have a bloom filter.

getHeight

public final int getHeight()

The height of a B+Tree. ZERO(0) means just a root leaf. Values greater than zero give the #of levels of abstract nodes. There is always one layer of leaves which is not included in this value.

Specified by:

getHeight in interface ICheckpoint

Returns:

The global depth and ZERO (0) unless the checkpoint record is for an IndexTypeEnum.BTree

See Also:

DumpJournal fails on non-BTree classes

getGlobalDepth

public final int getGlobalDepth()

The global depth of the root directory (HTree only).

Specified by:

getGlobalDepth in interface ICheckpoint

Returns:

The global depth and ZERO (0) unless the checkpoint record is for an IndexTypeEnum.HTree

See Also:

DumpJournal fails on non-BTree classes

getNodeCount

public final long getNodeCount()

Description copied from interface: ICheckpoint

The #of non-leaf nodes (B+Tree) or directories (HTree). This is ZERO (0) for a non-recursive data structure such as a solution set stream.

Specified by:

getNodeCount in interface ICheckpoint

getLeafCount

public final long getLeafCount()

Description copied from interface: ICheckpoint

The #of leaves (B+Tree), hash buckets (HTree), or ZERO (0) for a solution set stream.

Specified by:

getLeafCount in interface ICheckpoint

getEntryCount

public final long getEntryCount()

Description copied from interface: ICheckpoint

The #of index entries (aka tuple count).

Specified by:

getEntryCount in interface ICheckpoint

getCounter

public final long getCounter()

Description copied from interface: ICheckpoint

Return the value of the B+Tree local counter stored in the Checkpoint record.

Specified by:

getCounter in interface ICheckpoint

getRecordVersion

public final long getRecordVersion()

Description copied from interface: ICheckpoint

Return the value of the next record version number to be assigned that is stored in the Checkpoint record. This number is incremented each time a node or leaf is written onto the backing store. The initial value is ZERO (0). The first value assigned to a node or leaf will be ZERO (0).

Specified by:

getRecordVersion in interface ICheckpoint

getIndexType

public final IndexTypeEnum getIndexType()

Description copied from interface: ICheckpoint

The type of index for this checkpoint record.

Specified by:

getIndexType in interface ICheckpoint

toString

public final String toString()

A human readable representation of the state of the Checkpoint record.

Overrides:

toString in class Object

write

public final void write(IRawStore store)

Write the Checkpoint record on the store, setting addrCheckpoint as a side effect.

Parameters:

store -

Throws:

IllegalStateException - if the Checkpoint record has already been written.

load

public static Checkpoint load(IRawStore store,
              long addrCheckpoint)

Read a Checkpoint record from a store.

Parameters:

store - The store.

addrCheckpoint - The address from which to read the Checkpoint record. This address is set on the Checkpoint record as a side-effect.

readExternal

public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException

Specified by:

readExternal in interface Externalizable

Throws:

IOException

ClassNotFoundException

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

Specified by:

writeExternal in interface Externalizable

Throws:

IOException

loadFromCheckpoint

public static ICheckpointProtocol loadFromCheckpoint(IRawStore store,
                                     long checkpointAddr,
                                     boolean readOnly)

Utility method reads the Checkpoint record and then loads and returns a view of the associated read-only persistence capable data structure.

Note: The caller is responsible for marking the returned object as read-only or not depending on the context. This method should be used from trusted code such as Name2Addr and AbstractJournal which can make this decision.

Parameters:

store - The backing store.

checkpointAddr - The address of the checkpoint record.

readOnly - true if the object will be read-only.

Returns:

The persistence capable data structure loaded from that checkpoint.

create

public static ICheckpointProtocol create(IRawStore store,
                         IndexMetadata metadata)

Generic method to create a persistence capable data structure (GIST compatible, core implementation).

Parameters:

store - The backing store.

metadata - The metadata that describes the data structure to be created.

Returns:

The persistence capable data structure.