org.netbeans.mdr.persistence.btreeimpl.btreestorage

Class BtreeDatabase

java.lang.Object

org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeDatabase

All Implemented Interfaces:

MDRCache.OverflowHandler, Index, SinglevaluedIndex

public class BtreeDatabase
extends java.lang.Object
implements SinglevaluedIndex, MDRCache.OverflowHandler

This is the primary index for the btree implementation of Storage. It consists of three files:

The data file, with an extension of ".btd", which contains the serialized versions of the Streamable objects. This is accessed via the BtreeDatafile class.

The index file, with an extension of ".btx", which translates MOFIDs to the corresponding offset in the data file. This is accessed via the SinglevaluedBtree class.

The transactional log file has the extnsion ".btb". It exists only between the time a trasaction starts to be comitted and the time it is fully comitted or rolled back.

The data file contains enough information to regenerate the index file if the index file is lost or damaged. If the index file is missing when the btree database is opened, it is silently regenerated.

A Btree storage is transactional. This is implemented using the logging feature of the FileCache. Objects stored in a Btree storage have identity in memory. That is, fetching the same object multiple times will result in multiple references to the same object, not mutilple copies. This is implemented by MDRCache.

Performance of the Btree can be tuned by adjusting these parameters:

PAGE_SIZE is the size of the pages in the file cache.

FILE_CACHE_SIZE in the number of pages cached in memory. Increasing this will minimize the amount of reading done from the btree files, though at the cost of decreased memory for other purposes.

MDR_CACHE_SIZE is the number of currently unreferenced persistent objects kept in memory. Increasing this will reduce the number of reads done from the btree storage, though again at the cost of decreased memory for other purposes.

MDR_CACHE_THRESHHOLD is the number of changed objects to keep in memory before saving them to disk. Increasing this will reduce the amount of disk I/O done, though yet again at the cost of decreased memory for other purposes.

Method Summary

Methods

Modifier and Type	Method and Description
void	add(MOFID mKey, java.lang.Object value) Adds a repository record, throwing an exception if it already exists
void	add(java.lang.Object key, java.lang.Object value) Adds a repository record, throwing an exception if it already exists
void	cacheThreshholdReached(MDRCache cach, int size) cache has reached threshhold
int	checkConsistency(java.io.PrintWriter strm) Check consistency of btree database
void	commitChanges() Commits changes to transaction cache, if cache treshold is reached, flushes cache to disk.
void	compress() Compress repository.
java.lang.Object	get(MOFID mKey) Gets a record from the repository.
java.lang.Object	get(java.lang.Object key) Gets a record from the repository.
java.lang.Object	getIfExists(MOFID mKey) Gets a record from the repository.
java.lang.Object	getIfExists(java.lang.Object key) Gets a record from the repository.
Storage.EntryType	getKeyType() Returns the type of keys in index.
MofidGenerator	getMofidGenerator() Return the MOFID generator for this repository
java.util.Map	getMofidMap() Return the map of MOFID UUIDs we know about
java.lang.String	getName() Returns the unique name of the index in the Storage.
java.lang.Object	getObject(java.lang.Object key, SinglevaluedIndex dummy) Like get, since we don't return keys
java.lang.Object	getObjectIfExists(java.lang.Object key, SinglevaluedIndex dummy) Like getIfExists, since we don't return keys
Storage.EntryType	getValueType() Returns the type of values indexed by this index.
java.util.Set	keySet() Returns a set view of the keys contained in this index.
java.lang.String[]	listIndexes() List all index names
void	objectStateChanged(MOFID mKey) Mark that the object has changed, and so needs to be saved on commit
void	objectStateChanged(java.lang.Object key) Mark that the object has changed, and so needs to be saved on commit
boolean	put(java.lang.Object key, java.lang.Object value) Adds or replaces a repository record
java.util.Collection	queryByKeyPrefix(java.lang.Object prefix, SinglevaluedIndex repos) Returns a collection view of Map.Entry key-value pairs in the index, where key matches the queried prefix.
boolean	remove(MOFID mKey) Deletes a repository record based on a MOFID
boolean	remove(java.lang.Object key) Deletes a repository record
void	replace(MOFID mKey, java.lang.Object value) Replaces the original value associated with the specified key in this index with new value.
void	replace(java.lang.Object key, java.lang.Object value) Replaces the original value associated with the specified key in this index with new value.
void	rollbackChanges() roll back all changes
void	saveChanges() save all changes to disk without comitting
void	setLoggingStream(java.io.PrintStream strm) Set our logging stream
void	shutDown() Called on exit, commited data cached in transaction cache need to be written to disk.
int	size() returns the number of objects in the repository
java.util.Collection	values() Returns a collection view of the values contained in the repository.

Methods inherited from class java.lang.Object

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

Method Detail

compress

public void compress()
              throws StorageException

Compress repository. We do this by copying to a temporary repository, deleting the current repository, and renaming the temporary repository to our name.

Throws:

StorageException

size

public int size()

returns the number of objects in the repository

getName

public java.lang.String getName()

Returns the unique name of the index in the Storage.

Specified by:

getName in interface Index

Returns:

base file name for repository

getValueType

public Storage.EntryType getValueType()

Returns the type of values indexed by this index.

Specified by:

getValueType in interface Index

Returns:

EntryType.STREAMABLE

getKeyType

public Storage.EntryType getKeyType()

Returns the type of keys in index.

Specified by:

getKeyType in interface Index

Returns:

EntryType.MOFID

cacheThreshholdReached

public void cacheThreshholdReached(MDRCache cach,
                          int size)
                            throws StorageException

cache has reached threshhold

Specified by:

cacheThreshholdReached in interface MDRCache.OverflowHandler

Parameters:

cach - cache which reached threshhold

size - number of changed objects currently in cache

Throws:

StorageException

commitChanges

public void commitChanges()
                   throws StorageException

Commits changes to transaction cache, if cache treshold is reached, flushes cache to disk.

Throws:

StorageException

shutDown

public void shutDown()
              throws StorageException

Called on exit, commited data cached in transaction cache need to be written to disk.

Throws:

StorageException

saveChanges

public void saveChanges()
                 throws StorageException

save all changes to disk without comitting

Throws:

StorageException

rollbackChanges

public void rollbackChanges()
                     throws StorageException

roll back all changes

Throws:

StorageException

remove

public boolean remove(java.lang.Object key)
               throws StorageException

Deletes a repository record

Specified by:

remove in interface Index

Parameters:

key - -- a String

Returns:

true if record exists

Throws:

StorageException

remove

public boolean remove(MOFID mKey)
               throws StorageException

Deletes a repository record based on a MOFID

Parameters:

mKey -

Returns:

true if record exists

Throws:

StorageException

add

public void add(java.lang.Object key,
       java.lang.Object value)
         throws StorageException

Adds a repository record, throwing an exception if it already exists

Specified by:

add in interface Index

Parameters:

key - -- a String

value -

Throws:

StorageException

add

public void add(MOFID mKey,
       java.lang.Object value)
         throws StorageException

Adds a repository record, throwing an exception if it already exists

Parameters:

mKey -

value -

Throws:

StorageException

replace

public void replace(java.lang.Object key,
           java.lang.Object value)
             throws StorageException

Replaces the original value associated with the specified key in this index with new value. If no value was associated with this key prior to this call StorageBadRequestException is thrown.

Specified by:

replace in interface SinglevaluedIndex

Parameters:

key -

value -

Throws:

StorageException

StorageBadRequestException

replace

public void replace(MOFID mKey,
           java.lang.Object value)
             throws StorageException

Replaces the original value associated with the specified key in this index with new value. If no value was associated with this key prior to this call StorageBadRequestException is thrown.

Parameters:

mKey -

value -

Throws:

StorageException

put

public boolean put(java.lang.Object key,
          java.lang.Object value)
            throws StorageException

Adds or replaces a repository record

Specified by:

put in interface SinglevaluedIndex

Parameters:

key - -- a String

value -

Returns:

always null

Throws:

StorageException

getIfExists

public java.lang.Object getIfExists(java.lang.Object key)
                             throws StorageException

Gets a record from the repository. Returns null if none exists.

Specified by:

getIfExists in interface SinglevaluedIndex

Parameters:

key - -- a String

Returns:

value associated with specified key, or null if there was no mapping for key

Throws:

StorageException

getObjectIfExists

public java.lang.Object getObjectIfExists(java.lang.Object key,
                                 SinglevaluedIndex dummy)
                                   throws StorageException

Like getIfExists, since we don't return keys

Specified by:

getObjectIfExists in interface SinglevaluedIndex

Returns:

Throws:

StorageException

getIfExists

public java.lang.Object getIfExists(MOFID mKey)
                             throws StorageException

Gets a record from the repository. Returns null if none exists.

Parameters:

key -

Returns:

value associated with specified key, or null if there was no mapping for key

Throws:

StorageException

get

public java.lang.Object get(java.lang.Object key)
                     throws StorageException

Gets a record from the repository. Throws an exception if none exists.

Specified by:

get in interface SinglevaluedIndex

Parameters:

key -

Returns:

value associated with specified key, or null if there was no mapping for key

Throws:

StorageException

StorageBadRequestException

getObject

public java.lang.Object getObject(java.lang.Object key,
                         SinglevaluedIndex dummy)
                           throws StorageException

Like get, since we don't return keys

Specified by:

getObject in interface SinglevaluedIndex

Returns:

Throws:

StorageException

get

public java.lang.Object get(MOFID mKey)
                     throws StorageException

Gets a record from the repository. Throws an exception if none exists.

Parameters:

mKey -

Returns:

value associated with specified key, or null if there was no mapping for key

Throws:

StorageException

queryByKeyPrefix

public java.util.Collection queryByKeyPrefix(java.lang.Object prefix,
                                    SinglevaluedIndex repos)

Description copied from interface: SinglevaluedIndex

Returns a collection view of Map.Entry key-value pairs in the index, where key matches the queried prefix. Values are objects (as returned by getObject method).

Specified by:

queryByKeyPrefix in interface SinglevaluedIndex

Parameters:

prefix - queried prefix

repos - primary index

Returns:

objectStateChanged

public void objectStateChanged(java.lang.Object key)
                        throws StorageException

Mark that the object has changed, and so needs to be saved on commit

Parameters:

key - key of object whch changed (a String)

Throws:

StorageException

objectStateChanged

public void objectStateChanged(MOFID mKey)
                        throws StorageException

Mark that the object has changed, and so needs to be saved on commit

Parameters:

mKey - key of object whch changed

Throws:

StorageException

listIndexes

public java.lang.String[] listIndexes()
                               throws StorageException

List all index names

Returns:

an array of all the index names in alphabetical order

Throws:

StorageException

keySet

public java.util.Set keySet()
                     throws StorageException

Returns a set view of the keys contained in this index. Returned collection is read only and may not be modified.

Specified by:

keySet in interface Index

Returns:

the set of all MOFIDs which are keys for the repository

Throws:

StorageException

values

public java.util.Collection values()
                            throws StorageException

Returns a collection view of the values contained in the repository. Returned collection is read only and may not be modified.

Specified by:

values in interface SinglevaluedIndex

Returns:

all objects stored in the repository

Throws:

StorageException

setLoggingStream

public void setLoggingStream(java.io.PrintStream strm)

Set our logging stream

getMofidGenerator

public MofidGenerator getMofidGenerator()

Return the MOFID generator for this repository

getMofidMap

public java.util.Map getMofidMap()

Return the map of MOFID UUIDs we know about

checkConsistency

public int checkConsistency(java.io.PrintWriter strm)
                     throws StorageException

Check consistency of btree database

Parameters:

strm - where to write inconsistencies

Returns:

number of errors encountered

Throws:

StorageException