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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 methods, 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 parameter is a variable
to be initialized. The data parameter 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 parameter 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 parameters must have been previously initialized by a call
to DB_MULTIPLE_INIT. The retdata parameter is set to
refer to the next data element in the returned set, and the
retdlen parameter 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 parameter 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 parameter is a DBT structure returned from a
successful call to DBcursor->c_get for which the DB_MULTIPLE_KEY
flag was specified. The pointer and data parameters must
have been previously initialized by a call to DB_MULTIPLE_INIT.
The retkey parameter is set to refer to the next key element in
the returned set, and the retklen parameter is set to the length,
in bytes, of that key element. The retdata parameter is set to
refer to the next data element in the returned set, and the
retdlen parameter is set to the length, in bytes, of that data
element. The pointer parameter 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 parameter is a DBT structure returned from a
successful call to DBcursor->c_get for which the DB_MULTIPLE_KEY
flag was specified. The pointer and data parameters must
have been previously initialized by a call to DB_MULTIPLE_INIT.
The recno parameter is set to the record number of the next
record in the returned set. The retdata parameter is set to
refer to the next data element in the returned set, and the
retdlen parameter 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 parameter is set to NULL if there are no more key/data
pairs in the returned set.
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