SecondaryDatabase (Sleepycat Software, Inc. - Berkeley DB Java API)
Keywords: com.sleepycat.db.SecondaryDatabase class

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## com.sleepycat.db
Class SecondaryDatabase

    java.lang.Object
      com.sleepycat.db.Database
          com.sleepycat.db.SecondaryDatabase

public class SecondaryDatabase
extends Database

A secondary database handle.

Secondary databases are opened with `Environment.openSecondaryDatabase` and are always associated with a single primary database. The distinguishing characteristics of a secondary database are:

- Records are automatically added to a secondary database when records are added, modified and deleted in the primary database. Direct calls to `put()` methods on a secondary database are prohibited.
- The `delete` method of a secondary database will delete the primary record and as well as all its associated secondary records.
- Calls to all `get()` methods will return the data from the associated primary database.
- Additional `get()` method signatures are provided to return the primary key in an additional `pKey` parameter.
- Calls to `openCursor` will return a `SecondaryCursor`, which itself has `get()` methods that return the data of the primary database and additional `get()` method signatures for returning the primary key.
- The `openSecondaryCursor` method is provided to return a `SecondaryCursor` that doesn't require casting.

Before opening or creating a secondary database you must implement the SecondaryKeyCreator interface. For example:

        class MyKeyCreator implements SecondaryKeyCreator {
            public boolean createSecondaryKey(SecondaryDatabase secondary,
                                            DatabaseEntry key,
                                            DatabaseEntry data,
                                            DatabaseEntry result)
                    throws DatabaseException {
               //
               // DO HERE: Extract the secondary key from the primary key and data,
               // and set the secondary key into the result parameter.
               //
                return true;
            }
        }

To create a secondary database that supports duplicates:

        Database primaryDb; // The primary database must already be open.
        SecondaryConfig secConfig = new SecondaryConfig();
        secConfig.setAllowCreate(true);
        secConfig.setSortedDuplicates(true);
        secConfig.setKeyCreator(new MyKeyCreator());
        SecondaryDatabase newDb = env.openSecondaryDatabase(txn, "foo",
            primaryDb, secConfig)

If a primary database is to be associated with one or more secondary databases, it may not be configured for duplicates.

Constructor Summary
`SecondaryDatabase(String fileName, String databaseName, Database primaryDatabase, SecondaryConfig config)` Open a database.

Method Summary
`OperationStatus` | `get(Transaction txn, DatabaseEntry key, DatabaseEntry pKey, DatabaseEntry data, LockMode lockMode)` Retrieves the key/data pair with the given key.
`Database` | `getPrimaryDatabase()` Returns the primary database associated with this secondary database.
`OperationStatus` | `getSearchBoth(Transaction txn, DatabaseEntry key, DatabaseEntry pKey, DatabaseEntry data, LockMode lockMode)` Retrieves the key/data pair with the specified secondary and primary key, that is, both the primary and secondary key items must match.
`OperationStatus` | `getSearchRecordNumber(Transaction txn, DatabaseEntry key, DatabaseEntry pKey, DatabaseEntry data, LockMode lockMode)` Retrieves the key/data pair associated with the specific numbered record of the database.
`SecondaryConfig` | `getSecondaryConfig()` Returns a copy of the secondary configuration of this database.
`SecondaryCursor` | `openSecondaryCursor(Transaction txn, CursorConfig cursorConfig)` Obtain a cursor on a database, returning a `SecondaryCursor`.

Methods inherited from class com.sleepycat.db.Database
`append, close, close, consume, delete, get, getCacheFile, getConfig, getDatabaseFile, getDatabaseName, getEnvironment, getKeyRange, getSearchBoth, getSearchRecordNumber, getStats, join, openCursor, openSequence, put, putNoDupData, putNoOverwrite, remove, removeSequence, rename, setConfig, sync, truncate, upgrade, verify`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### SecondaryDatabase

    public SecondaryDatabase(String fileName,
                             String databaseName,
                             Database primaryDatabase,
                             SecondaryConfig config)
                      throws DatabaseException,
                             FileNotFoundException

  Open a database.

  The database is represented by the file and database parameters.

  The currently supported database file formats (or access methods) are Btree, Hash, Queue, and Recno. The Btree format is a representation of a sorted, balanced tree structure. The Hash format is an extensible, dynamic hashing scheme. The Queue format supports fast access to fixed-length records accessed sequentially or by logical record number. The Recno format supports fixed- or variable-length records, accessed sequentially or by logical record number, and optionally backed by a flat text file.

  Storage and retrieval are based on key/data pairs; see `DatabaseEntry` for more information.

  Opening a database is a relatively expensive operation, and maintaining a set of open databases will normally be preferable to repeatedly opening and closing the database for each new query.

  In-memory databases never intended to be preserved on disk may be created by setting both the fileName and databaseName parameters to null. Note that in-memory databases can only ever be shared by sharing the single database handle that created them, in circumstances where doing so is safe. The environment variable `TMPDIR` may be used as a directory in which to create temporary backing files.

Parameters:
  `fileName` - The name of an underlying file that will be used to back the database. On Windows platforms, this argument will be interpreted as a UTF-8 string, which is equivalent to ASCII for Latin characters.

  `databaseName` - An optional parameter that allows applications to have multiple databases in a single file. Although no databaseName parameter needs to be specified, it is an error to attempt to open a second database in a physical file that was not initially created using a databaseName parameter. Further, the databaseName parameter is not supported by the Queue format.

  `primaryDatabase` - a database handle for the primary database that is to be indexed.

  `config` - The secondary database open attributes. If null, default attributes are used.

Method Detail

### getSecondaryConfig

    public SecondaryConfig getSecondaryConfig()
                                       throws DatabaseException

  Returns a copy of the secondary configuration of this database.

  Returns:
    a copy of the secondary configuration of this database.

  Throws:
    `DatabaseException` - if a failure occurs.

### get

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

  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.

  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 secondary key used as input. It must be initialized with a non-null byte array by the caller.

    `pKey` - the primary key returned as output. Its byte array does not need to be initialized by the caller.

    `data` - the primary 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.

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

  Throws:
    `DeadlockException` - if the operation was selected to resolve a deadlock.

    `IllegalArgumentException` - if an invalid parameter was specified.

    `DatabaseException` - if a failure occurs.

### getSearchBoth

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

  Retrieves the key/data pair with the specified secondary and primary key, that is, both the primary and secondary key items must match.

  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 secondary key used as input. It must be initialized with a non-null byte array by the caller.
    `pKey` - the primary key used as input. It must be initialized with a non-null byte array by the caller.
    `data` - the primary 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.

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

  Throws:
    `DeadlockException` - if the operation was selected to resolve a deadlock.

    `IllegalArgumentException` - if an invalid parameter was specified.

    `DatabaseException` - if a failure occurs.

### getPrimaryDatabase

    public Database getPrimaryDatabase()
                                throws DatabaseException

  Returns the primary database associated with this secondary database.

  Returns:
    the primary database associated with this secondary database.

  Throws:
    `DatabaseException` - if a failure occurs.

### openSecondaryCursor

    public SecondaryCursor openSecondaryCursor(Transaction txn,
                                               CursorConfig cursorConfig)
                                        throws DatabaseException

  Obtain a cursor on a database, returning a `SecondaryCursor`. Calling this method is the equivalent of calling `Database.openCursor(com.sleepycat.db.Transaction, com.sleepycat.db.CursorConfig)` and casting the result to `SecondaryCursor`.

  Parameters:
    `txn` - To use a cursor for writing to a transactional database, an explicit transaction must be specified. For read-only access to a transactional database, the transaction may be null. For a non-transactional database, the transaction must be null.

    To transaction-protect cursor operations, cursors must be opened and closed within the context of a transaction, and the txn parameter specifies the transaction context in which the cursor will be used.

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

  Returns:
    A secondary database cursor.

  Throws:
    `DatabaseException` - if a failure occurs.

### getSearchRecordNumber

    public OperationStatus getSearchRecordNumber(Transaction txn,
                                                 DatabaseEntry key,
                                                 DatabaseEntry pKey,
                                                 DatabaseEntry data,
                                                 LockMode lockMode)
                                          throws DatabaseException

  Retrieves the key/data pair associated with the specific numbered record of the database.

  The data field of the specified key must be a byte array containing a record number, as described in `DatabaseEntry`. This determines the record to be retrieved.

  For this method to be called, the underlying database must be of type Btree, and it must have been configured to support record numbers.

  If this method fails for any reason, the position of the cursor will be unchanged.

  Parameters:
    `key` - the secondary key returned as output. Its byte array does not need to be initialized by the caller.
    `pKey` - the primary key returned as output. Its byte array does not need to be initialized by the caller.
    `data` - the primary data returned as output. Multiple results can be retrieved by passing an object that is a subclass of `MultipleEntry`, otherwise its byte array does not need to be initialized by the caller.
    `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:
    `NullPointerException` - if a DatabaseEntry parameter is null or does not contain a required non-null byte array.

    `DeadlockException` - if the operation was selected to resolve a deadlock.

    `IllegalArgumentException` - if an invalid parameter was specified.

    `DatabaseException` - if a failure occurs.

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Copyright (c) 1996-2004 Sleepycat Software, Inc. - All rights reserved.