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Berkeley DB: DBT
DBT: Bulk Retrieval
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If either of the DB_MULTIPLE or DB_MULTIPLE_KEY flags
were specified to the DB->get or DBcursor->c_get functions, the data
DBT returned by those interfaces will refer to a buffer that
is filled with data. Access to that data is through the following
macros:
- DB_MULTIPLE_INIT
DB_MULTIPLE_INIT(void *pointer, DBT *data);
Initialize the retrieval. The pointer argument is a variable
to be initialized. The data argument is a DBT structure
returned from a successful call to DB->get or DBcursor->c_get
for which one of the DB_MULTIPLE or DB_MULTIPLE_KEY
flags was specified.
- DB_MULTIPLE_NEXT
DB_MULTIPLE_NEXT(void *pointer, DBT *data, void *retdata, size_t retdlen);
The data argument is a DBT structure returned from a
successful call to DB->get or DBcursor->c_get for which the
DB_MULTIPLE flag was specified. The pointer and
data arguments must have been previously initialized by a call
to DB_MULTIPLE_INIT. The retdata argument is set to
refer to the next data element in the returned set, and the
retdlen argument is set to the length, in bytes, of that data
element. When used with the Queue and Recno access methods,
retdata will be set to NULL for deleted records. The
pointer argument is set to NULL if there are no more data
elements in the returned set.
- DB_MULTIPLE_KEY_NEXT
DB_MULTIPLE_KEY_NEXT(void *pointer, DBT *data,
void *retkey, size_t retklen, void *retdata, size_t retdlen);
The data argument is a DBT structure returned from a
successful call to DB->get or DBcursor->c_get for which the
DB_MULTIPLE_KEY flag was specified. The pointer and
data arguments must have been previously initialized by a call
to DB_MULTIPLE_INIT. The retkey argument is set to
refer to the next key element in the returned set, and the
retklen argument is set to the length, in bytes, of that key
element. The retdata argument is set to refer to the next data
element in the returned set, and the retdlen argument is set to
the length, in bytes, of that data element. The pointer
argument is set to NULL if there are no more key/data pairs in the
returned set.
- DB_MULTIPLE_RECNO_NEXT
DB_MULTIPLE_RECNO_NEXT(void *pointer, DBT *data,
db_recno_t recno, void * retdata, size_t retdlen);
The data argument is a DBT structure returned from a
successful call to DB->get or DBcursor->c_get for which the
DB_MULTIPLE_KEY flag was specified. The pointer and
data arguments must have been previously initialized by a call
to DB_MULTIPLE_INIT. The recno argument is set to the
record number of the next record in the returned set. The
retdata argument is set to refer to the next data element in
the returned set, and the retdlen argument is set to the length,
in bytes, of that data element. When used with the Queue and Recno
access methods, retdata will be set to NULL for deleted
records. The pointer argument is set to NULL if there are
no more key/data pairs in the returned set.
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