int DB->get(DB *db, DB_TXN *txnid, DBT *key, DBT *data, u_int32_t flags);
int DB->pget(DB *db, DB_TXN *txnid, DBT *key, DBT *pkey, DBT *data, u_int32_t flags);
The DB->get method retrieves key/data pairs from the database. The address and length of the data associated with the specified key are returned in the structure to which data refers.
In the presence of duplicate key values, DB->get will return the first data item for the designated key. Duplicates are sorted by insert order, except where this order has been overridden by cursor operations. Retrieval of duplicates requires the use of cursor operations. See DBcursor->c_get for details.
When called on a database that has been made into a secondary index using the DB->associate method, the DB->get and DB->pget methods return the key from the secondary index and the data item from the primary database. In addition, the DB->pget method returns the key from the primary database. In databases that are not secondary indices, the DB->pget method will always fail.
The DB->get method will return DB_NOTFOUND if the specified key is not in the database. The DB->get method will return DB_KEYEMPTY if the database is a Queue or Recno database and the specified key exists, but was never explicitly created by the application or was later deleted. Unless otherwise specified, the DB->get method returns a non-zero error value on failure and 0 on success.
If lock or transaction timeouts have been specified, the DB->get method with the DB_CONSUME_WAIT flag may return DB_LOCK_NOTGRANTED. This failure, by itself, does not require the enclosing transaction be aborted.
When used with the DB->pget method version of this method on a secondary index handle, return the secondary key/primary key/data tuple only if both the primary and secondary keys match the arguments. It is an error to use the DB_GET_BOTH flag with the DB->get version of this method and a secondary index handle.
The data field of the specified key must be a pointer to a logical record number (that is, a db_recno_t). This record number determines the record to be retrieved.
For DB_SET_RECNO to be specified, the underlying database must be of type Btree, and it must have been created with the DB_RECNUM flag.
In the case of Btree or Hash databases, all of the data items associated with the specified key are entered into the buffer. In the case of Queue or Recno databases, all of the data items in the database, starting at, and subsequent to, the specified key, are entered into the buffer.
The buffer to which the data parameter refers must be provided from user memory (see DB_DBT_USERMEM). The buffer must be at least as large as the page size of the underlying database, aligned for unsigned integer access, and be a multiple of 1024 bytes in size. If the buffer size is insufficient, then upon return from the call the size field of the data parameter will have been set to an estimated buffer size, and the error DB_BUFFER_SMALL is returned. (The size is an estimate as the exact size needed may not be known until all entries are read. It is best to initially provide a relatively large buffer, but applications should be prepared to resize the buffer as necessary and repeatedly call the method.)
The DB_MULTIPLE flag may only be used alone, or with the DB_GET_BOTH and DB_SET_RECNO options. The DB_MULTIPLE flag may not be used when accessing databases made into secondary indices using the DB->associate method.
See DB_MULTIPLE_INIT for more information.
Because the DB->get method will not hold locks across Berkeley DB calls in non-transactional operations, the DB_RMW flag to the DB->get call is meaningful only in the presence of transactions.
The DB->get method may fail and return one of the following non-zero errors:
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