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<h1>Db.associate</h1>
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<h3><pre>
import com.sleepycat.db.*;
<p>
public interface DbSecondaryKeyCreate
{
public int
secondary_key_create(Db secondary, Dbt key, Dbt data Dbt result)
throws DbException;
}
public class Db
{
...
public int associate(Db secondary,
DbSecondaryKeyCreate secondary_key_create, int flags)
throws DbException;
...
}
</pre></h3>
<h1>Description</h1>
<p>The Db.associate function is used to declare one database a
secondary index for a primary database. After a secondary database has
been "associated" with a primary database, all updates to the primary
will be automatically reflected in the secondary and all reads from the
secondary will return corresponding data from the primary. Note that
as primary keys must be unique for secondary indices to work, the
primary database must be configured without support for duplicate data
items. See <a href="../../db4-devel-4.0.14/ref/am/second.html">Secondary indices</a> for
more information.
<p>The associate method called should be a method off a database handle for
the primary database that is to be indexed.
The <b>secondary</b> argument should be an open database handle of
either a newly created and empty database that is to be used to store
a secondary index, or of a database that was previously associated with
the same primary and contains a secondary index. Note that it is not
safe to associate as a secondary database a handle that is in use by
another thread of control or has open cursors. If the handle was opened
with the <a href="../../db4-devel-4.0.14/api_java/env_open.html#DB_THREAD">Db.DB_THREAD</a> flag it is safe to use it in multiple threads
of control after the Db.associate method has returned. Note also
that either secondary keys must be unique or the secondary database must
be configured with support for duplicate data items.
<p>The <b>callback</b> argument should refer to a callback function that
creates a secondary key from a given primary key and data pair. When
called, the first argument will be the secondary <a href="../../db4-devel-4.0.14/api_java/db_class.html">Db</a> handle; the
second and third arguments will be <a href="../../db4-devel-4.0.14/api_java/dbt_class.html">Dbt</a>s containing a primary
key and datum respectively; and the fourth argument will be a zeroed
DBT in which the callback function should fill in <b>data</b> and
<b>size</b> fields that describe the secondary key.
<a name="3"><!--meow--></a>
<a name="4"><!--meow--></a>
<p>If any key/data pair in the primary yields a null secondary key and
should be left out of the secondary index, the callback function may
optionally return Db.DB_DONOTINDEX. Otherwise, the callback
function should return 0 in case of success or any other integer error
code in case of failure; the error code will be returned from the Berkeley DB
interface call that initiated the callback. Note that if the callback
function returns Db.DB_DONOTINDEX for any key/data pairs in the
primary database, the secondary index will not contain any reference to
those key/data pairs, and such operations as cursor iterations and range
queries will reflect only the corresponding subset of the database. If
this is not desirable, the application should ensure that the callback
function is well-defined for all possible values and never returns
Db.DB_DONOTINDEX.
<p>The callback argument may be NULL if and only if both the primary and
secondary database handles were opened with the <a href="../../db4-devel-4.0.14/api_java/db_open.html#DB_RDONLY">Db.DB_RDONLY</a> flag.
<p>The <b>flags</b> value must be set to 0 or
the following value:
<p><dl compact>
<p><dt><a name="Db.DB_CREATE">Db.DB_CREATE</a><dd>If the secondary database is empty, walk through the primary and create
an index to it in the empty secondary. Note that this operation is
potentially very expensive.
<p>If the secondary database has been opened in an environment configured
with transactions, each put necessary for its creation will be done in
the context of a transaction created for the purpose.
<p>Note that care should be taken not to use a newly-created secondary
database in another thread of control until the Db.associate
call has returned successfully in the first thread.
</dl>
<h1>Errors</h1>
<p>The Db.associate method may fail and throw an exception encapsulating a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
<p>The secondary database handle has already been associated with this or
another database handle.
<p>The secondary database handle is not open.
<p>The primary database has been configured to allow duplicates.
</dl>
<p>The Db.associate method may fail and throw an exception for errors specified for other Berkeley DB and C library or system methods.
If a catastrophic error has occurred, the Db.associate method may fail and throw
a <a href="../../db4-devel-4.0.14/api_java/runrec_class.html">DbRunRecoveryException</a>, in which case all subsequent Berkeley DB calls
will fail in the same way.
<h1>Class</h1>
<a href="../../db4-devel-4.0.14/api_java/db_class.html">Db</a>
<h1>See Also</h1>
<a href="../../db4-devel-4.0.14/api_java/db_associate.html">Db.associate</a>,
<a href="../../db4-devel-4.0.14/api_java/db_close.html">Db.close</a>,
<a href="../../db4-devel-4.0.14/api_java/db_cursor.html">Db.cursor</a>,
<a href="../../db4-devel-4.0.14/api_java/db_del.html">Db.del</a>,
<a href="../../db4-devel-4.0.14/api_java/db_fd.html">Db.fd</a>,
<a href="../../db4-devel-4.0.14/api_java/db_get.html">Db.get</a>,
<a href="../../db4-devel-4.0.14/api_java/db_get.html">Db.pget</a>,
<a href="../../db4-devel-4.0.14/api_java/db_get_byteswapped.html">Db.get_byteswapped</a>,
<a href="../../db4-devel-4.0.14/api_java/db_get_type.html">Db.get_type</a>,
<a href="../../db4-devel-4.0.14/api_java/db_join.html">Db.join</a>,
<a href="../../db4-devel-4.0.14/api_java/db_key_range.html">Db.key_range</a>,
<a href="../../db4-devel-4.0.14/api_java/db_open.html">Db.open</a>,
<a href="../../db4-devel-4.0.14/api_java/db_put.html">Db.put</a>,
<a href="../../db4-devel-4.0.14/api_java/db_remove.html">Db.remove</a>,
<a href="../../db4-devel-4.0.14/api_java/db_rename.html">Db.rename</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_append_recno.html">Db.set_append_recno</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_bt_minkey.html">Db.set_bt_minkey</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_cachesize.html">Db.set_cachesize</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_errcall.html">Db.set_errcall</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_errpfx.html">Db.set_errpfx</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_feedback.html">Db.set_feedback</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_flags.html">Db.set_flags</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_h_ffactor.html">Db.set_h_ffactor</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_h_nelem.html">Db.set_h_nelem</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_lorder.html">Db.set_lorder</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_pagesize.html">Db.set_pagesize</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_q_extentsize.html">Db.set_q_extentsize</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_re_delim.html">Db.set_re_delim</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_re_len.html">Db.set_re_len</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_re_pad.html">Db.set_re_pad</a>,
<a href="../../db4-devel-4.0.14/api_java/db_set_re_source.html">Db.set_re_source</a>,
<a href="../../db4-devel-4.0.14/api_java/db_stat.html">Db.stat</a>,
<a href="../../db4-devel-4.0.14/api_java/db_sync.html">Db.sync</a>,
<a href="../../db4-devel-4.0.14/api_java/db_truncate.html">Db.truncate</a>,
<a href="../../db4-devel-4.0.14/api_java/db_upgrade.html">Db.upgrade</a>,
and
<a href="../../db4-devel-4.0.14/api_java/db_verify.html">Db.verify</a>.
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