Db::join
Db::join |
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#include <db_cxx.h>int Db::join(Dbc **curslist, Dbc **dbcp, u_int32_t flags);
The Db::join method creates a specialized cursor for use in performing equality or natural joins on secondary indices. For information on how to organize your data to use this functionality, see Equality join.
The primary argument contains the Db handle of the primary database, which is keyed by the data values found in entries in the curslist.
The curslist argument contains a NULL terminated array of cursors. Each cursor must have been initialized to refer to the key on which the underlying database should be joined. Typically, this initialization is done by a Dbc::get call with the DB_SET flag specified. Once the cursors have been passed as part of a curslist, they should not be accessed or modified until the newly created join cursor has been closed, or else inconsistent results may be returned.
Joined values are retrieved by doing a sequential iteration over the first cursor in the curslist argument, and a nested iteration over each secondary cursor in the order they are specified in the curslist argument. This requires database traversals to search for the current datum in all the cursors after the first. For this reason, the best join performance normally results from sorting the cursors from the one that refers to the least number of data items to the one that refers to the most. By default, Db::join does this sort on behalf of its caller.
The flags value must be set to 0 or the following value:
A newly created cursor is returned in the memory location to which dbcp refers. It supports only the Dbc::get and dbc_close cursor functions:
The flags value must be set to 0 or the following value:
In addition, the following flag may be set by bitwise inclusively OR'ing it into the flags parameter:
For the returned join cursor to be used in a transaction-protected manner, the cursors listed in curslist must have been created within the context of the same transaction.
The Db::join method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.
The Db::join method may fail and throw an exception or return a non-zero error for the following conditions:
Cursor functions other than Dbc::get or Dbc::close were called.
The Db::join method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the Db::join method may fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.
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Copyright Sleepycat Software
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If a catastrophic error has occurred, the Db::join method may fail and
either return DB_RUNRECOVERY or throw a
DbRunRecoveryException,
in which case all subsequent Berkeley DB calls will fail in the same way.
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Databases and Related Methods
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If a catastrophic error has occurred, the Db::join method may fail and either
return DB_RUNRECOVERY or throw an exception encapsulating
DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail
in the same way.
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Db::associate,
Db::close,
Db::cursor,
Db::del,
Db::err, Db::errx
Db::fd,
Db::get,
Db::pget,
Db::get_byteswapped,
Db::get_type,
Db::join,
Db::key_range,
Db::open,
Db::put,
Db::remove,
Db::rename,
Db::set_alloc,
Db::set_append_recno,
Db::set_bt_compare,
Db::set_bt_minkey,
Db::set_bt_prefix,
Db::set_cachesize,
Db::set_dup_compare,
Db::set_errcall,
Db::set_errfile,
Db::set_errpfx,
Db::set_feedback,
Db::set_flags,
Db::set_h_ffactor,
Db::set_h_hash,
Db::set_h_nelem,
Db::set_lorder,
Db::set_pagesize,
Db::set_paniccall,
Db::set_q_extentsize,
Db::set_re_delim,
Db::set_re_len,
Db::set_re_pad,
Db::set_re_source,
Db::stat,
Db::sync,
Db::truncate,
Db::upgrade,
and
Db::verify.
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1.1.1.5
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@Import: RPM 4.1.1
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@d1 2
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d109 4
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If a catastrophic error has occurred, the Db::join method may fail and
either return DB_RUNRECOVERY or throw a
DbRunRecoveryException,
in which case all subsequent Berkeley DB calls will fail in the same way.
d116 45
a160 1
Databases and Related Methods
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