Berkeley DB: Db::cursor
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++

# Db::cursor |

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    #include <db_cxx.h>

    int
    Db::cursor(DbTxn *txnid, Dbc **cursorp, u_int32_t flags);

# Description

The Db::cursor method creates a cursor and copies a pointer to it into the memory to which cursorp refers.

If the operation is to be transaction-protected, the txnid parameter is a transaction handle returned from DbEnv::txn_begin; otherwise, NULL.

To transaction-protect cursor operations, cursors must be opened and closed within the context of a transaction, and the txnid parameter specifies the transaction context in which the cursor may be used.

The flags value must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:

DB_DIRTY_READ
  All read operations performed by the cursor may return modified but not yet committed data. Silently ignored if the DB_DIRTY_READ flag was not specified when the underlying database was opened.

DB_WRITECURSOR
  Specify that the cursor will be used to update the database. The underlying database environment must have been opened using the DB_INIT_CDB flag.

The Db::cursor 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.

# Errors

The Db::cursor method may fail and throw an exception or return a non-zero error for the following conditions:

EINVAL
  An invalid flag value or parameter was specified.

The Db::cursor 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::cursor 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.

# Class

Dbc

# See Also

Database Cursors and Related Methods`

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