com.sleepycat.je

Class Database

java.lang.Object

com.sleepycat.je.Database

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

SecondaryDatabase

public class Database
extends java.lang.Object
implements java.io.Closeable

A database handle.

Database attributes are specified in the DatabaseConfig class. Database handles are free-threaded and may be used concurrently by multiple threads.

To open an existing database with default attributes:

     Environment env = new Environment(home, null);
     Database myDatabase = env.openDatabase(null, "mydatabase", null);
 

To create a transactional database that supports duplicates:

     DatabaseConfig dbConfig = new DatabaseConfig();
     dbConfig.setTransactional(true);
     dbConfig.setAllowCreate(true);
     dbConfig.setSortedDuplicates(true);
     Database db = env.openDatabase(txn, "mydatabase", dbConfig);
 

Method Summary

Modifier and Type	Method and Description
void	close() Discards the database handle.
int	compareDuplicates(DatabaseEntry entry1, DatabaseEntry entry2) Compares two data elements using either the default comparator if no duplicate comparator has been set or the duplicate comparator if one has been set.
int	compareKeys(DatabaseEntry entry1, DatabaseEntry entry2) Compares two keys using either the default comparator if no BTree comparator has been set or the BTree comparator if one has been set.
long	count() Counts the key/data pairs in the database.
long	count(long memoryLimit) Counts the key/data pairs in the database.
OperationStatus	delete(Transaction txn, DatabaseEntry key) Removes records with a given key from the database.
OperationResult	delete(Transaction txn, DatabaseEntry key, WriteOptions options) Removes records with a given key from the database.
OperationResult	get(Transaction txn, DatabaseEntry key, DatabaseEntry data, Get getType, ReadOptions options) Retrieves a record according to the specified Get type.
OperationStatus	get(Transaction txn, DatabaseEntry key, DatabaseEntry data, LockMode lockMode) Retrieves the key/data pair with the given key.
DatabaseConfig	getConfig() Returns this Database object's configuration.
java.lang.String	getDatabaseName() Returns the database name.
Environment	getEnvironment() Returns the Environment handle for the database environment underlying the Database.
OperationStatus	getSearchBoth(Transaction txn, DatabaseEntry key, DatabaseEntry data, LockMode lockMode) Retrieves the key/data pair with the given key and data value, that is, both the key and data items must match.
java.util.List<SecondaryDatabase>	getSecondaryDatabases() Returns a list of all SecondaryDatabase objects associated with a primary database.
DatabaseStats	getStats(StatsConfig config) Returns database statistics.
JoinCursor	join(Cursor[] cursors, JoinConfig config) Creates a specialized join cursor for use in performing equality or natural joins on secondary indices.
DiskOrderedCursor	openCursor(DiskOrderedCursorConfig cursorConfig) Create a DiskOrderedCursor to iterate over the records in 'this' Database.
Cursor	openCursor(Transaction txn, CursorConfig cursorConfig) Returns a cursor into the database.
Sequence	openSequence(Transaction txn, DatabaseEntry key, SequenceConfig config) Opens a sequence in the database.
void	preload(long maxBytes) Deprecated. As of JE 2.0.83, replaced by preload(PreloadConfig).
void	preload(long maxBytes, long maxMillisecs) Deprecated. As of JE 2.0.101, replaced by preload(PreloadConfig).
PreloadStats	preload(PreloadConfig config) Preloads the cache.
OperationStatus	put(Transaction txn, DatabaseEntry key, DatabaseEntry data) Stores the key/data pair into the database.
OperationResult	put(Transaction txn, DatabaseEntry key, DatabaseEntry data, Put putType, WriteOptions options) Inserts or updates a record according to the specified Put type.
OperationStatus	putNoDupData(Transaction txn, DatabaseEntry key, DatabaseEntry data) Stores the key/data pair into the database if it does not already appear in the database.
OperationStatus	putNoOverwrite(Transaction txn, DatabaseEntry key, DatabaseEntry data) Stores the key/data pair into the database if the key does not already appear in the database.
void	removeSequence(Transaction txn, DatabaseEntry key) Removes the sequence from the database.
void	sync() Flushes any cached information for this database to disk; only applicable for deferred-write databases.
DatabaseStats	verify(VerifyConfig config) Verifies the integrity of the database.

Methods inherited from class java.lang.Object

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

Method Detail

close

public void close()

Discards the database handle.

When closing the last open handle for a deferred-write database, any cached database information is flushed to disk as if sync() were called.

The database handle should not be closed while any other handle that refers to it is not yet closed; for example, database handles should not be closed while cursor handles into the database remain open, or transactions that include operations on the database have not yet been committed or aborted. Specifically, this includes Cursor and Transaction handles.

When multiple threads are using the Database handle concurrently, only a single thread may call this method.

When called on a database that is the primary database for a secondary index, the primary database should be closed only after all secondary indices which reference it have been closed.

The database handle may not be accessed again after this method is called, regardless of the method's success or failure, with one exception: the close method itself may be called any number of times.

WARNING: To guard against memory leaks, the application should discard all references to the closed handle. While BDB makes an effort to discard references from closed objects to the allocated memory for an environment, this behavior is not guaranteed. The safe course of action for an application is to discard all references to closed BDB objects.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Throws:

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if cursors associated with this database are still open.

See Also:

DatabaseConfig.setDeferredWrite

sync

public void sync()

Flushes any cached information for this database to disk; only applicable for deferred-write databases.

Note that deferred-write databases are automatically flushed to disk when the close() method is called.

Throws:

DatabasePreemptedException - in a replicated environment if the master has truncated, removed or renamed the database.

OperationFailureException - if this exception occurred earlier and caused the transaction to be invalidated.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this is not a deferred-write database, or this database is read-only.

java.lang.IllegalStateException - if the database has been closed.

See Also:

DatabaseConfig.setDeferredWrite

openSequence

public Sequence openSequence(Transaction txn,
                             DatabaseEntry key,
                             SequenceConfig config)

Opens a sequence in the database.

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - The key DatabaseEntry of the sequence.

config - The sequence attributes. If null, default attributes are used.

Returns:

a new Sequence handle.

Throws:

SequenceExistsException - if the sequence record already exists and the SequenceConfig ExclusiveCreate parameter is true.

SequenceNotFoundException - if the sequence record does not exist and the SequenceConfig AllowCreate parameter is false.

OperationFailureException - if one of the Read Operation Failures occurs. If the sequence does not exist and the AllowCreate parameter is true, then one of the Write Operation Failures may also occur.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this database is read-only, or this database is configured for duplicates.

java.lang.IllegalStateException - if the Sequence record is deleted by another thread during this method invocation, or the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified, for example, an invalid SequenceConfig parameter.

removeSequence

public void removeSequence(Transaction txn,
                           DatabaseEntry key)

Removes the sequence from the database. This method should not be called if there are open handles on this sequence.

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - The key DatabaseEntry of the sequence.

Throws:

OperationFailureException - if one of the Write Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this database is read-only.

openCursor

public Cursor openCursor(Transaction txn,
                         CursorConfig cursorConfig)

Returns a cursor into the database.

Parameters:

txn - the transaction used to protect all operations performed with the cursor, or null if the operations should not be transaction protected. If the database is non-transactional, null must be specified. For a transactional database, the transaction is optional for read-only access and required for read-write access.

cursorConfig - The cursor attributes. If null, default attributes are used.

Returns:

A database cursor.

Throws:

DatabasePreemptedException - in a replicated environment if the master has truncated, removed or renamed the database.

OperationFailureException - if this exception occurred earlier and caused the transaction to be invalidated.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified, for example, an invalid CursorConfig parameter.

openCursor

public DiskOrderedCursor openCursor(DiskOrderedCursorConfig cursorConfig)

Create a DiskOrderedCursor to iterate over the records in 'this' Database. Because the retrieval is based on Log Sequence Number (LSN) order rather than key order, records are returned in unsorted order in exchange for generally faster retrieval. LSN order approximates disk sector order.

See DiskOrderedCursor for more details and a description of the consistency guarantees provided by the scan.

WARNING: After calling this method, deletion of log files by the JE log cleaner will be disabled until DiskOrderedCursor.close() is called. To prevent unbounded growth of disk usage, be sure to call DiskOrderedCursor.close() to re-enable log file deletion.

delete

public OperationResult delete(Transaction txn,
                              DatabaseEntry key,
                              WriteOptions options)

Removes records with a given key from the database. In the presence of duplicate keys, all records associated with the given key will be removed. When the database has associated secondary databases, this method also deletes the associated index records.

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - the key used as input.

options - the WriteOptions, or null to use default options.

Returns:

the OperationResult if the record is deleted, else null if the given key was not found in the database.

Throws:

OperationFailureException - if one of the Write Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this database is read-only.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified. This includes passing a null input key parameter, an input key parameter with a null data array, or a partial key input parameter.

Since:

7.0

delete

public OperationStatus delete(Transaction txn,
                              DatabaseEntry key)

Removes records with a given key from the database. In the presence of duplicate keys, all records associated with the given key will be removed. When the database has associated secondary databases, this method also deletes the associated index records.

Calling this method is equivalent to calling delete(Transaction, DatabaseEntry, WriteOptions).

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - the key used as input.

Returns:

The method will return OperationStatus.NOTFOUND if the given key is not found in the database; otherwise OperationStatus.SUCCESS.

Throws:

OperationFailureException - if one of the Write Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this database is read-only.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified. This includes passing a null input key parameter, an input key parameter with a null data array, or a partial key input parameter.

get

public OperationResult get(Transaction txn,
                           DatabaseEntry key,
                           DatabaseEntry data,
                           Get getType,
                           ReadOptions options)

Retrieves a record according to the specified Get type.

If the operation succeeds, the record will be locked according to the lock mode specified, the key and/or data will be returned via the (non-null) DatabaseEntry parameters, and a non-null OperationResult will be returned. If the operation fails because the record requested is not found, null is returned.

The following table lists each allowed operation and whether the key and data parameters are input or output parameters. See the individual Get operations for more information.

Get operation	Description	'key' parameter	'data' parameter
Get.SEARCH	Searches using an exact match by key.	input	output
Get.SEARCH_BOTH	Searches using an exact match by key and data.	input	input

Parameters:

txn - For a transactional database, an explicit transaction may be specified to transaction-protect the operation, or null may be specified to perform the operation without transaction protection. For a non-transactional database, null must be specified.

key - the key input parameter.

data - the data input or output parameter, depending on getType.

getType - the Get operation type. May not be null.

options - the ReadOptions, or null to use default options.

Returns:

the OperationResult if the record requested is found, else null.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified. This includes passing a null getType, a null input key/data parameter, an input key/data parameter with a null data array, and a partial key/data input parameter.

Since:

7.0

get

public OperationStatus get(Transaction txn,
                           DatabaseEntry key,
                           DatabaseEntry data,
                           LockMode lockMode)

Retrieves the key/data pair with the given key. If the matching key has duplicate values, the first data item in the set of duplicates is returned. Retrieval of duplicates requires the use of Cursor operations.

Calling this method is equivalent to calling get(Transaction, DatabaseEntry, DatabaseEntry, Get, ReadOptions) with Get.SEARCH.

Parameters:

txn - For a transactional database, an explicit transaction may be specified to transaction-protect the operation, or null may be specified to perform the operation without transaction protection. For a non-transactional database, null must be specified.

key - the key used as input.

data - the data returned as output.

lockMode - the locking attributes; if null, default attributes are used.

Returns:

OperationStatus.NOTFOUND if no matching key/data pair is found; otherwise, OperationStatus.SUCCESS.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified.

getSearchBoth

public OperationStatus getSearchBoth(Transaction txn,
                                     DatabaseEntry key,
                                     DatabaseEntry data,
                                     LockMode lockMode)

Retrieves the key/data pair with the given key and data value, that is, both the key and data items must match.

Calling this method is equivalent to calling get(Transaction, DatabaseEntry, DatabaseEntry, Get, ReadOptions) with Get.SEARCH_BOTH.

Parameters:

txn - For a transactional database, an explicit transaction may be specified to transaction-protect the operation, or null may be specified to perform the operation without transaction protection. For a non-transactional database, null must be specified.

key - the key used as input.

data - the data used as input.

lockMode - the locking attributes; if null, default attributes are used.

Returns:

OperationStatus.NOTFOUND if no matching key/data pair is found; otherwise, OperationStatus.SUCCESS.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified.

put

public OperationResult put(Transaction txn,
                           DatabaseEntry key,
                           DatabaseEntry data,
                           Put putType,
                           WriteOptions options)

Inserts or updates a record according to the specified Put type.

If the operation succeeds, the record will be locked according to the lock mode specified, the cursor will be positioned on the record, and a non-null OperationResult will be returned. If the operation fails because the record already exists (or does not exist, depending on the putType), null is returned.

When the database has associated secondary databases, this method also inserts or deletes associated index records as necessary.

The following table lists each allowed operation. See the individual Put operations for more information.

Put operation	Description	Returns null when?	Other special rules
Put.OVERWRITE	Inserts or updates a record depending on whether a matching record is already present.	Never returns null.	Without duplicates, a matching record is one with the same key; with duplicates, it is one with the same key and data.
Put.NO_OVERWRITE	Inserts a record if a record with a matching key is not already present.	When an existing record matches.	If the database has duplicate keys, a record is inserted only if there are no records with a matching key.
Put.NO_DUP_DATA	Inserts a record in a database with duplicate keys if a record with a matching key and data is not already present.	When an existing record matches.	Without duplicates, this operation is not allowed.

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - the key used as input.

data - the data used as input.

putType - the Put operation type. May not be null.

options - the WriteOptions, or null to use default options.

Returns:

the OperationResult if the record is written, else null.

Throws:

OperationFailureException - if one of the Write Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if the database is read-only, or putType is Put.NO_DUP_DATA and the database is not configured for duplicates.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified. This includes passing a null putType, a null input key/data parameter, an input key/data parameter with a null data array, a partial key/data input parameter, or when putType is Put.CURRENT.

Since:

7.0

put

public OperationStatus put(Transaction txn,
                           DatabaseEntry key,
                           DatabaseEntry data)

Stores the key/data pair into the database.

Calling this method is equivalent to calling put(Transaction, DatabaseEntry, DatabaseEntry, Put, WriteOptions) with Put.OVERWRITE.

If the key already appears in the database and duplicates are not configured, the data associated with the key will be replaced. If the key already appears in the database and sorted duplicates are configured, the new data value is inserted at the correct sorted location.

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - the key used as input..

data - the data used as input.

Returns:

OperationStatus.SUCCESS.

Throws:

OperationFailureException - if one of the Write Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this database is read-only.

java.lang.IllegalStateException - if the database has been closed.

putNoOverwrite

public OperationStatus putNoOverwrite(Transaction txn,
                                      DatabaseEntry key,
                                      DatabaseEntry data)

Stores the key/data pair into the database if the key does not already appear in the database.

Calling this method is equivalent to calling put(Transaction, DatabaseEntry, DatabaseEntry, Put, WriteOptions) with Put.NO_OVERWRITE.

This method will return OpeationStatus.KEYEXIST if the key already exists in the database, even if the database supports duplicates.

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - the key used as input..

data - the data used as input.

Returns:

OperationStatus.KEYEXIST if the key already appears in the database, else OperationStatus.SUCCESS

Throws:

OperationFailureException - if one of the Write Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this database is read-only.

java.lang.IllegalStateException - if the database has been closed.

putNoDupData

public OperationStatus putNoDupData(Transaction txn,
                                    DatabaseEntry key,
                                    DatabaseEntry data)

Stores the key/data pair into the database if it does not already appear in the database.

Calling this method is equivalent to calling put(Transaction, DatabaseEntry, DatabaseEntry, Put, WriteOptions) with Put.NO_DUP_DATA.

This method may only be called if the underlying database has been configured to support sorted duplicates.

Parameters:

txn - For a transactional database, an explicit transaction may be specified, or null may be specified to use auto-commit. For a non-transactional database, null must be specified.

key - the key used as input..

data - the data used as input.

Returns:

OperationStatus.KEYEXIST if the key/data pair already appears in the database, else OperationStatus.SUCCESS

Throws:

OperationFailureException - if one of the Write Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.UnsupportedOperationException - if this database is not configured for duplicates, or this database is read-only.

java.lang.IllegalStateException - if the database has been closed.

join

public JoinCursor join(Cursor[] cursors,
                       JoinConfig config)

Creates a specialized join cursor for use in performing equality or natural joins on secondary indices.

Each cursor in the cursors array must have been initialized to refer to the key on which the underlying database should be joined. Typically, this initialization is done by calling Cursor.getSearchKey.

Once the cursors have been passed to this method, they should not be accessed or modified until the newly created join cursor has been closed, or else inconsistent results may be returned. However, the position of the cursors will not be changed by this method or by the methods of the join cursor.

Parameters:

cursors - an array of cursors associated with this primary database.

config - The join attributes. If null, default attributes are used.

Returns:

a specialized cursor that returns the results of the equality join operation.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified, for example, an invalid JoinConfig parameter.

See Also:

JoinCursor

preload

public void preload(long maxBytes)

Deprecated. As of JE 2.0.83, replaced by preload(PreloadConfig).

Preloads the cache. This method should only be called when there are no operations being performed on the database in other threads. Executing preload during concurrent updates may result in some or all of the tree being loaded into the JE cache. Executing preload during any other types of operations may result in JE exceeding its allocated cache size. preload() effectively locks the entire database and therefore will lock out the checkpointer, cleaner, and compressor, as well as not allow eviction to occur.

Parameters:

maxBytes - The maximum number of bytes to load. If maxBytes is 0, je.evictor.maxMemory is used.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

preload

public void preload(long maxBytes,
                    long maxMillisecs)

Deprecated. As of JE 2.0.101, replaced by preload(PreloadConfig).

Preloads the cache. This method should only be called when there are no operations being performed on the database in other threads. Executing preload during concurrent updates may result in some or all of the tree being loaded into the JE cache. Executing preload during any other types of operations may result in JE exceeding its allocated cache size. preload() effectively locks the entire database and therefore will lock out the checkpointer, cleaner, and compressor, as well as not allow eviction to occur.

Parameters:

maxBytes - The maximum number of bytes to load. If maxBytes is 0, je.evictor.maxMemory is used.

maxMillisecs - The maximum time in milliseconds to use when preloading. Preloading stops once this limit has been reached. If maxMillisecs is 0, preloading can go on indefinitely or until maxBytes (if non-0) is reached.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

preload

public PreloadStats preload(PreloadConfig config)

Preloads the cache. This method should only be called when there are no operations being performed on the database in other threads. Executing preload during concurrent updates may result in some or all of the tree being loaded into the JE cache. Executing preload during any other types of operations may result in JE exceeding its allocated cache size. preload() effectively locks the entire database and therefore will lock out the checkpointer, cleaner, and compressor, as well as not allow eviction to occur. If the database is replicated and the environment is in the replica state, then the replica may become temporarily disconnected from the master if the replica needs to replay changes against the database and is locked out because the time taken by the preload operation exceeds ReplicationConfig.FEEDER_TIMEOUT.

While this method preloads a single database, Environment.preload(com.sleepycat.je.Database[], com.sleepycat.je.PreloadConfig) lets you preload multiple databases.

Parameters:

config - The PreloadConfig object that specifies the parameters of the preload.

Returns:

A PreloadStats object with various statistics about the preload() operation.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if PreloadConfig.getMaxBytes is greater than size of the JE cache.

count

public long count()

Counts the key/data pairs in the database. This operation is faster than obtaining a count from a cursor based scan of the database, and will not perturb the current contents of the cache. However, the count is not guaranteed to be accurate if there are concurrent updates. Note that this method does scan a significant portion of the database and should be considered a fairly expensive operation.

This operation uses the an internal infrastructure and algorithm that is similar to the one used for the DiskOrderedCursor. Specifically, it will disable deletion of log files by the JE log cleaner during its execution and will consume a certain amount of memory (but without affecting the memory that is available for the JE cache). To avoid excessive memory consumption (and a potential OutOfMemoryError) this method places an internal limit on its memory consumption. If this limit is reached, the method will still work properly, but its performance will degrade. To specify a different memory limit than the one used by this method, use the count(long memoryLimit) method.

Currently, the internal memory limit is calculated as 10% of the difference between the max JVM memory (the value returned by Runtime.getRuntime().maxMemory()) and the configured JE cache size.

Returns:

The count of key/data pairs in the database.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

See Also:

Cache Statistics: Unexpected Sizes

count

public long count(long memoryLimit)

Counts the key/data pairs in the database. This operation is faster than obtaining a count from a cursor based scan of the database, and will not perturb the current contents of the cache. However, the count is not guaranteed to be accurate if there are concurrent updates. Note that this method does scan a significant portion of the database and should be considered a fairly expensive operation.

This operation uses the an internal infrastructure and algorithm that is similar to the one used for the DiskOrderedCursor. Specifically, it will disable deletion of log files by the JE log cleaner during its execution and will consume a certain amount of memory (but without affecting the memory that is available for the JE cache). To avoid excessive memory consumption (and a potential OutOfMemoryError) this method takes as input an upper bound on the memory it may consume. If this limit is reached, the method will still work properly, but its performance will degrade.

Parameters:

memoryLimit - The maximum memory (in bytes) that may be consumed by this method.

Returns:

The count of key/data pairs in the database.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

See Also:

Cache Statistics: Unexpected Sizes

getStats

public DatabaseStats getStats(StatsConfig config)

Returns database statistics.

If this method has not been configured to avoid expensive operations (using the StatsConfig.setFast method), it will access some of or all the pages in the database, incurring a severe performance penalty as well as possibly flushing the underlying cache.

In the presence of multiple threads or processes accessing an active database, the information returned by this method may be out-of-date.

Parameters:

config - The statistics returned; if null, default statistics are returned.

Returns:

Database statistics.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

verify

public DatabaseStats verify(VerifyConfig config)

Verifies the integrity of the database.

Verification is an expensive operation that should normally only be used for troubleshooting and debugging.

Parameters:

config - Configures the verify operation; if null, the default operation is performed.

Returns:

Database statistics.

Throws:

OperationFailureException - if one of the Read Operation Failures occurs.

EnvironmentFailureException - if a corruption is detected, or if an unexpected, internal or environment-wide failure occurs. If a persistent corruption is detected, EnvironmentFailureException.isCorrupted() will return true.

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if an invalid parameter is specified.

getDatabaseName

public java.lang.String getDatabaseName()

Returns the database name.

This method may be called at any time during the life of the application.

Returns:

The database name.

Throws:

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

getConfig

public DatabaseConfig getConfig()

Returns this Database object's configuration.

This may differ from the configuration used to open this object if the database existed previously.

Unlike most Database methods, this method may be called after the database is closed.

Returns:

This Database object's configuration.

Throws:

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

java.lang.IllegalStateException - if the database has been closed.

getEnvironment

public Environment getEnvironment()

Returns the Environment handle for the database environment underlying the Database.

This method may be called at any time during the life of the application.

Returns:

The Environment handle for the database environment underlying the Database.

getSecondaryDatabases

public java.util.List<SecondaryDatabase> getSecondaryDatabases()

Returns a list of all SecondaryDatabase objects associated with a primary database.

If no secondaries are associated with this database, an empty list is returned.

compareKeys

public int compareKeys(DatabaseEntry entry1,
                       DatabaseEntry entry2)

Compares two keys using either the default comparator if no BTree comparator has been set or the BTree comparator if one has been set.

Returns:

-1 if entry1 compares less than entry2, 0 if entry1 compares equal to entry2, 1 if entry1 compares greater than entry2

Throws:

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if either entry is a partial DatabaseEntry, or is null.

compareDuplicates

public int compareDuplicates(DatabaseEntry entry1,
                             DatabaseEntry entry2)

Compares two data elements using either the default comparator if no duplicate comparator has been set or the duplicate comparator if one has been set.

Returns:

-1 if entry1 compares less than entry2, 0 if entry1 compares equal to entry2, 1 if entry1 compares greater than entry2

Throws:

java.lang.IllegalStateException - if the database has been closed.

java.lang.IllegalArgumentException - if either entry is a partial DatabaseEntry, or is null.