#include <db_cxx.h>

int
DbSequence::get(DbTxn *txnid, int32_t delta, db_seq_t *retp, u_int32_t flags);

Description: DbSequence::get

The DbSequence::get method returns the next available element in the sequence and changes the sequence value by delta. The value of delta must be greater than zero. If there are enough cached values in the sequence handle then they will be returned. Otherwise the next value will be fetched from the database and incremented (decremented) by enough to cover the delta and the next batch of cached values.

If the underlying database handle was opened in a transaction then either the txnid parameter must be a valid transaction handle or DB_AUTO_COMMIT must be specified. The txnid handle must be NULL if the sequence handle was opened with a non-zero cache size.

For maximum concurrency a non-zero cache size should be specified prior to opening the sequence handle and DB_AUTO_COMMIT | DB_TXN_NOSYNC should be specified each DbSequence::get method call.

The DbSequence::get method will return EINVAL if the record in the database is not a valid sequence record, or the sequences have overflowed is range.

Parameters

delta

Specifies the amount to increment or decrement the sequence.

flags

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

DB_AUTO_COMMIT

If the database must be updated the update will be enclosed in a transaction and will be recoverable.

DB_TXN_NOSYNC

If a DB_AUTO_COMMIT triggers a transaction, do not synchronously flush the log.

retp

retp points to the memory to hold the return value from the sequence.

txnid

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

Class

See Also