DbSequence::get

API Ref

#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.

For maximum concurrency a non-zero cache size should be specified prior to opening the sequence handle and 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_TXN_NOSYNC
If the operation is implicitly transaction protected (the txnid argument is NULL but the operation occurs to a transactional database), do not synchronously flush the log when the transaction commits.
retp
retp points to the memory to hold the return value from the sequence.
txnid
If the operation is part of an application-specified transaction, the txnid parameter is a transaction handle returned from DbEnv::txn_begin; otherwise NULL. If no transaction handle is specified, but the operation occurs in a transactional database, the operation will be implicitly transaction protected. The txnid handle must be NULL if the sequence handle was opened with a non-zero cache size.

Class

DbSequence

See Also

Sequences and Related Methods

APIRef

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