com.sleepycat.je.Cursor
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Berkeley DB Java Edition version 5.0.34 |
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java.lang.Object
public class Cursor
A database cursor. Cursors are used for operating on collections of records, for iterating over a database, and for saving handles to individual records, so that they can be modified after they have been read.
Cursors which are opened with a transaction instance are transactional cursors and may be used by multiple threads, but only serially. That is, the application must serialize access to the handle. Non-transactional cursors, opened with a null transaction instance, may not be used by multiple threads.
If the cursor is to be used to perform operations on behalf of a transaction, the cursor must be opened and closed within the context of that single transaction.
Once the cursor close() method has been called, the handle may not
be accessed again, regardless of the close method's success or
failure, with one exception: the close method itself may be called
any number of times to simplify error handling.
To obtain a cursor with default attributes:
Cursor cursor = myDatabase.openCursor(txn, null);
To customize the attributes of a cursor, use a CursorConfig object.
CursorConfig config = new CursorConfig();
config.setReadUncommitted(true);
Cursor cursor = myDatabase.openCursor(txn, config);
Modifications to the database during a sequential scan will be reflected in the scan; that is, records inserted behind a cursor will not be returned while records inserted in front of a cursor will be returned.
The DatabaseEntry Partial property can
be used to optimize in certain cases. This provides varying degrees of
performance benefits that depend on the specific operation and use of READ_UNCOMMITTED isolation, as described below.
When retrieving a record with a Database or Cursor
method, if only the key is needed by the application then the retrieval of
the data item can be suppressed using the Partial property. If setPartial(0, 0, true) is called for the DatabaseEntry passed as
the data parameter, the data item will not be returned by the Database or Cursor method.
Suppressing the return of the data item potentially has a large
performance benefit when the READ_UNCOMMITTED isolation mode is
used. In this case, if the record data is not in the JE cache, it will not
be read from disk. The performance benefit is potentially large because
random access disk reads may be reduced. Examples are:
READ_UNCOMMITTED isolation is acceptable.READ_UNCOMMITTED isolation.For other isolation modes (READ_COMMITTED, REPEATABLE_READ and SERIALIZABLE), the performance benefit is
not as significant. In this case, the data item must be read into the JE
cache if it is not already present, in order to lock the record. The only
performance benefit is that the data will not be copied from the JE cache to
the application's entry parameter.
For information on specifying isolation modes, see LockMode,
CursorConfig and TransactionConfig.
The Partial property may also be used to retrieve or update only a
portion of a data item. This avoids copying the entire record between the
JE cache and the application data parameter. However, this feature is not
currently fully optimized, since the entire record is always read or written
to the database, and the entire record is cached. A partial update may
be performed only with Cursor.putCurrent.
In limited cases, the Partial property may also be used to retrieve a
partial key item. For example, a DatabaseEntry with a Partial
property may be passed to getNext. However, in practice
this has limited value since the entire key is usually needed by the
application, and the benefit of copying a portion of the key is generally
very small. Partial key items may not be passed to methods that use the key
as an input parameter, for example, getSearchKey. In
general, the usefulness of partial key items is very limited.
| Method Summary | |
|---|---|
void |
close()
Discards the cursor. |
int |
count()
Returns a count of the number of data items for the key to which the cursor refers. |
long |
countEstimate()
Returns a rough estimate of the count of the number of data items for the key to which the cursor refers. |
OperationStatus |
delete()
Deletes the key/data pair to which the cursor refers. |
Cursor |
dup(boolean samePosition)
Returns a new cursor with the same transaction and locker ID as the original cursor. |
CacheMode |
getCacheMode()
Returns the CacheMode used for subsequent operations performed
using this cursor. |
CursorConfig |
getConfig()
Returns this cursor's configuration. |
OperationStatus |
getCurrent(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Returns the key/data pair to which the cursor refers. |
Database |
getDatabase()
Returns the Database handle associated with this Cursor. |
OperationStatus |
getFirst(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the first key/data pair of the database, and returns that pair. |
OperationStatus |
getLast(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the last key/data pair of the database, and returns that pair. |
OperationStatus |
getNext(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the next key/data pair and returns that pair. |
OperationStatus |
getNextDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
If the next key/data pair of the database is a duplicate data record for the current key/data pair, moves the cursor to the next key/data pair of the database and returns that pair. |
OperationStatus |
getNextNoDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the next non-duplicate key/data pair and returns that pair. |
OperationStatus |
getPrev(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the previous key/data pair and returns that pair. |
OperationStatus |
getPrevDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
If the previous key/data pair of the database is a duplicate data record for the current key/data pair, moves the cursor to the previous key/data pair of the database and returns that pair. |
OperationStatus |
getPrevNoDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the previous non-duplicate key/data pair and returns that pair. |
OperationStatus |
getSearchBoth(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the specified key/data pair, where both the key and data items must match. |
OperationStatus |
getSearchBothRange(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the specified key and closest matching data item of the database. |
OperationStatus |
getSearchKey(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the given key of the database, and returns the datum associated with the given key. |
OperationStatus |
getSearchKeyRange(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Moves the cursor to the closest matching key of the database, and returns the data item associated with the matching key. |
OperationStatus |
put(DatabaseEntry key,
DatabaseEntry data)
Stores a key/data pair into the database. |
OperationStatus |
putCurrent(DatabaseEntry data)
Replaces the data in the key/data pair at the current cursor position. |
OperationStatus |
putNoDupData(DatabaseEntry key,
DatabaseEntry data)
Stores a key/data pair into the database. |
OperationStatus |
putNoOverwrite(DatabaseEntry key,
DatabaseEntry data)
Stores a key/data pair into the database. |
void |
setCacheMode(CacheMode cacheMode)
Sets the CacheMode used for subsequent operations performed
using this cursor. |
long |
skipNext(long maxCount,
DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Skips forward a given number of key/data pairs and returns the number by which the cursor is moved. |
long |
skipPrev(long maxCount,
DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
Skips backward a given number of key/data pairs and returns the number by which the cursor is moved. |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Method Detail |
|---|
public Database getDatabase()
getDatabase in interface ForwardCursorpublic CursorConfig getConfig()
This may differ from the configuration used to open this object if the cursor existed previously.
public CacheMode getCacheMode()
CacheMode used for subsequent operations performed
using this cursor. If setCacheMode(com.sleepycat.je.CacheMode) has not been called with a
non-null value, the configured Database or Environment default is
returned.
CacheMode used for subsequent operations using
this cursor.setCacheMode(com.sleepycat.je.CacheMode)public void setCacheMode(CacheMode cacheMode)
CacheMode used for subsequent operations performed
using this cursor. This method may be used to override the defaults
specified using DatabaseConfig.setCacheMode(com.sleepycat.je.CacheMode) and EnvironmentMutableConfig.setCacheMode(com.sleepycat.je.CacheMode).
cacheMode - is the CacheMode used for subsequent operations
using this cursor, or null to configure the Database or Environment
default.for further details.
public void close()
throws DatabaseException
The cursor handle may not be used again after this method has been called, regardless of the method's success or failure.
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.
close in interface ForwardCursorclose in interface CloseableEnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
DatabaseException
public int count()
throws DatabaseException
If the database is configured for duplicates, the database is scanned
internally, without taking any record locks, to count the number of
non-deleted entries. Although the internal scan is more efficient under
some conditions, the result is the same as if a cursor were used to
iterate over the entries using LockMode.READ_UNCOMMITTED.
If the database is not configured for duplicates, the count returned is always zero or one, depending on the record at the cursor position is deleted or not.
The cost of this method is directly proportional to the number of records scanned.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
DatabaseException
public long countEstimate()
throws DatabaseException
If the database is configured for duplicates, a quick estimate of the
number of records is computed using information in the Btree. Because
the Btree is unbalanced, in some cases the estimate may be off by a
factor of two or more. The estimate is accurate when the number of
records is less than the configured NodeMaxEntries.
If the database is not configured for duplicates, the count returned is always zero or one, depending on the record at the cursor position is deleted or not.
The cost of this method is fixed, rather than being proportional to
the number of records scanned. Because its accuracy is variable, this
method should normally be used when accuracy is not required, such as
for query optimization, and a fixed cost operation is needed. For
example, this method is used internally for determining the index
processing order in a JoinCursor.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
DatabaseException
public Cursor dup(boolean samePosition)
throws DatabaseException
This is useful when an application is using locking and requires two or more cursors in the same thread of control.
samePosition - If true, the newly created cursor is initialized
to refer to the same position in the database as the original cursor
(if any) and hold the same locks (if any). If false, or the original
cursor does not hold a database position and locks, the returned
cursor is uninitialized and will behave like a newly created cursor.
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.
IllegalStateException - if the cursor or database has been closed.
DatabaseException
public OperationStatus delete()
throws LockConflictException,
DatabaseException,
UnsupportedOperationException
When called on a cursor opened on a database that has been made into a secondary index, this method the key/data pair from the primary database and all secondary indices.
The cursor position is unchanged after a delete, and subsequent calls to cursor functions expecting the cursor to refer to an existing key will fail.
OperationStatus.KEYEMPTY if the key/pair at the cursor position has
been deleted; otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Write
Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
UnsupportedOperationException - if the database is transactional
but this cursor was not opened with a non-null transaction parameter,
or the database is read-only.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
LockConflictException
DatabaseException
public OperationStatus put(DatabaseEntry key,
DatabaseEntry data)
throws DatabaseException,
UnsupportedOperationException
If the put method succeeds, the cursor is always positioned to refer to the newly inserted item. If the put method fails for any reason, the state of the cursor will be unchanged.
If the key already appears in the database and duplicates are supported, the new data value is inserted at the correct sorted location. If the key already appears in the database and duplicates are not supported, the data associated with the key will be replaced.
key - the key DatabaseEntry operated on.data - the data DatabaseEntry stored.
OperationFailureException - if one of the Write
Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
UnsupportedOperationException - if the database is transactional
but this cursor was not opened with a non-null transaction parameter,
or the database is read-only.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus putNoOverwrite(DatabaseEntry key,
DatabaseEntry data)
throws DatabaseException,
UnsupportedOperationException
If the putNoOverwrite method succeeds, the cursor is always positioned to refer to the newly inserted item. If the putNoOverwrite method fails for any reason, the state of the cursor will be unchanged.
If the key already appears in the database, putNoOverwrite will
return OperationStatus.KEYEXIST.
key - the key DatabaseEntry operated on.data - the data DatabaseEntry stored.
OperationFailureException - if one of the Write
Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
UnsupportedOperationException - if the database is transactional
but this cursor was not opened with a non-null transaction parameter,
or the database is read-only.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus putNoDupData(DatabaseEntry key,
DatabaseEntry data)
throws DatabaseException,
UnsupportedOperationException
If the putNoDupData method succeeds, the cursor is always positioned to refer to the newly inserted item. If the putNoDupData method fails for any reason, the state of the cursor will be unchanged.
Insert the specified key/data pair into the database, unless a
key/data pair comparing equally to it already exists in the database.
If a matching key/data pair already exists in the database, OperationStatus.KEYEXIST is
returned.
key - the key DatabaseEntry
operated on.data - the data DatabaseEntry stored.
OperationFailureException - if one of the Write
Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
UnsupportedOperationException - if the database is transactional
but this cursor was not opened with a non-null transaction parameter, or
the database is read-only, or the database is not configured for
duplicates.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus putCurrent(DatabaseEntry data)
throws DatabaseException,
UnsupportedOperationException
Whether the putCurrent method succeeds or fails for any reason, the state of the cursor will be unchanged.
Overwrite the data of the key/data pair to which the cursor refers with the specified data item. This method will return OperationStatus.NOTFOUND if the cursor currently refers to an already-deleted key/data pair.
For a database that does not support duplicates, the data may be
changed by this method. If duplicates are supported, the data may be
changed only if a custom partial comparator is configured and the
comparator considers the old and new data to be equal (that is, the
comparator returns zero). For more information on partial comparators
see DatabaseConfig.setDuplicateComparator(java.util.Comparator.
If the old and new data are unequal according to the comparator, a
DuplicateDataException is thrown. Changing the data in this
case would change the sort order of the record, which would change the
cursor position, and this is not allowed. To change the sort order of a
record, delete it and then re-insert it.
data - - the data DatabaseEntry stored.
A partial data item may be
specified to optimize for partial data update.
OperationStatus.KEYEMPTY if the key/pair at the cursor position has
been deleted; otherwise, OperationStatus.SUCCESS.
DuplicateDataException - if the old and new data are not equal
according to the configured duplicate comparator or default comparator.
OperationFailureException - if one of the Write
Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
UnsupportedOperationException - if the database is transactional
but this cursor was not opened with a non-null transaction parameter,
or the database is read-only.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getCurrent(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
getCurrent in interface ForwardCursorkey - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.KEYEMPTY if the key/pair at the cursor position has
been deleted; otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getFirst(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getLast(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getNext(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If the cursor is not yet initialized, move the cursor to the first key/data pair of the database, and return that pair. Otherwise, the cursor is moved to the next key/data pair of the database, and that pair is returned. In the presence of duplicate key values, the value of the key may not change.
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
getNext in interface ForwardCursorkey - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getNextDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getNextNoDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If the cursor is not yet initialized, move the cursor to the first key/data pair of the database, and return that pair. Otherwise, the cursor is moved to the next non-duplicate key of the database, and that key/data pair is returned.
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getPrev(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If the cursor is not yet initialized, move the cursor to the last key/data pair of the database, and return that pair. Otherwise, the cursor is moved to the previous key/data pair of the database, and that pair is returned. In the presence of duplicate key values, the value of the key may not change.
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getPrevDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getPrevNoDup(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If the cursor is not yet initialized, move the cursor to the last key/data pair of the database, and return that pair. Otherwise, the cursor is moved to the previous non-duplicate key of the database, and that key/data pair is returned.
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public long skipNext(long maxCount,
DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
Without regard to performance, calling this method is equivalent to
repeatedly calling getNext with LockMode.READ_UNCOMMITTED to skip over the desired number of key/data
pairs, and then calling getCurrent with the lockMode parameter to return the final key/data pair.
With regard to performance, this method is optimized to skip over
key/value pairs using a smaller number of Btree operations. When there
is no contention on the bottom internal nodes (BINs) and all BINs are in
cache, the number of Btree operations is reduced by roughly two orders
of magnitude, where the exact number depends on the EnvironmentConfig.NODE_MAX_ENTRIES setting. When there is contention
on BINs or fetching BINs is required, the scan is broken up into smaller
operations to avoid blocking other threads for long time periods.
If the returned count is greater than zero, then the key/data pair at the new cursor position is also returned. If zero is returned, then there are no key/value pairs that follow the cursor position and a key/data pair is not returned.
If this method fails for any reason or if zero is returned, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
maxCount - the maximum number of key/data pairs to skip, i.e., the
maximum number by which the cursor should be moved; must be greater
than zero.key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public long skipPrev(long maxCount,
DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
Without regard to performance, calling this method is equivalent to
repeatedly calling getPrev with LockMode.READ_UNCOMMITTED to skip over the desired number of key/data
pairs, and then calling getCurrent with the lockMode parameter to return the final key/data pair.
With regard to performance, this method is optimized to skip over
key/value pairs using a smaller number of Btree operations. When there
is no contention on the bottom internal nodes (BINs) and all BINs are in
cache, the number of Btree operations is reduced by roughly two orders
of magnitude, where the exact number depends on the EnvironmentConfig.NODE_MAX_ENTRIES setting. When there is contention
on BINs or fetching BINs is required, the scan is broken up into smaller
operations to avoid blocking other threads for long time periods.
If the returned count is greater than zero, then the key/data pair at the new cursor position is also returned. If zero is returned, then there are no key/value pairs that follow the cursor position and a key/data pair is not returned.
If this method fails for any reason or if zero is returned, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
maxCount - the maximum number of key/data pairs to skip, i.e., the
maximum number by which the cursor should be moved; must be greater
than zero.key - the key returned as output. Its byte array does not need to
be initialized by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the cursor is uninitialized (not positioned on a record), or the
non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getSearchKey(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key used as input. It must be initialized with a
non-null byte array by the caller.data - the data returned as output. Its byte array does not need
to be initialized by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getSearchKeyRange(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
The returned key/data pair is for the smallest key greater than or equal to the specified key (as determined by the key comparison function), permitting partial key matches and range searches.
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key used as input and returned as output. It must be
initialized with a non-null byte array by the caller.
A partial data item may be
specified to optimize for key only or partial data retrieval.data - the data returned as output. Its byte array does not need
to be initialized by the caller.lockMode - the locking attributes; if null, default attributes
are used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getSearchBoth(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key used as input. It must be initialized with a
non-null byte array by the caller.data - the data used as input. It must be initialized with a
non-null byte array by the caller.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
public OperationStatus getSearchBothRange(DatabaseEntry key,
DatabaseEntry data,
LockMode lockMode)
throws DatabaseException
In the case of any database supporting sorted duplicate sets, the returned key/data pair is for the smallest data item greater than or equal to the specified data item (as determined by the duplicate comparison function), permitting partial matches and range searches in duplicate data sets.
If this method fails for any reason, the position of the cursor will be unchanged.
In a replicated environment, an explicit transaction must have been
specified when opening the cursor, unless read-uncommitted isolation is
specified via the CursorConfig or LockMode
parameter.
key - the key used as input and returned as output. It must be
initialized with a non-null byte array by the caller.data - the data used as input and returned as output. It must be
initialized with a non-null byte array by the caller.lockMode - the locking attributes; if null, default attributes are
used. LockMode.READ_COMMITTED is not allowed.
OperationStatus.NOTFOUND if no matching key/data pair is found;
otherwise, OperationStatus.SUCCESS.
OperationFailureException - if one of the Read Operation
Failures occurs.
EnvironmentFailureException - if an unexpected, internal or
environment-wide failure occurs.
IllegalStateException - if the cursor or database has been closed,
or the non-transactional cursor was created in a different thread.
IllegalArgumentException - if an invalid parameter is specified.
DatabaseException
|
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