Jena TDB, Transactions and Writes

[Laurent Pellegrino <la...@gmail.com>]

Hello all,

I wonder whether bunch of quadruples are buffered in memory before to be
written out to disk all at once? I remember a message about such a feature
but I cannot find it back. If yes, are buffered writes performed per write
transaction or also inter write-transactions?

Kind Regards,

Laurent

Re: Jena TDB, Transactions and Writes

[Andy Seaborne <an...@apache.org>]

On 11/12/12 16:32, Laurent Pellegrino wrote:
> Hello all,
>
> I wonder whether bunch of quadruples are buffered in memory before to be
> written out to disk all at once? I remember a message about such a feature
> but I cannot find it back. If yes, are buffered writes performed per write
> transaction or also inter write-transactions?
>
> Kind Regards,
>
> Laurent
>

In a transaction, the changes are currently kept in-memory until a 
prepare is done at which point the node table is written (as it's an 
append-only datastructure, you don't need to wait for "commit").  Small 
matter of scalability here but it matters a lot less than I expected 
especially a the node table can be appended to early on.

At commit time, the indexes are written to the journal.  Because all 
writes are done at the same time, the OS should be able to optimize the 
write ordering.

	Andy