Hi Michael, Thanks. I was hoping that the ML journals would contain only the transaction (i.e. action) logs. That way it, i feel it would it fast.
However, Ron mentioned that the journal contains the delta data already. So, to me, deriving the delta data would take a bit longer than just recording the actions. Just my thoughts. Regards, Danny On Fri, Apr 20, 2012 at 12:40 PM, Michael Blakeley <[email protected]>wrote: > Danny, http://en.wikipedia.org/wiki/Transaction_log might be useful > background reading. A similar technique is used by every ACID-compliant > database that I am familiar with. > > -- Mike > > On 20 Apr 2012, at 06:37 , Ron Hitchens wrote: > > > > > The journal certainly does contain the data. It > > records the deltas to the database. That means that > > when an update request runs, all the changes it made > > to the state of the database are recorded in the journal. > > Those changes can be applied again from the journal, > > without running the request again. > > > > Updates can be additions, replacements or deletions > > of documents (fragments actually, which are not always > > 1-1 with documents). > > > > It's the journal that protects you from outages. > > Writing journal frames is as efficient as it possibly > > can be. There is some overhead to write to the journal, > > but that's the cost of insuring that when a transaction > > commit completes, it is guaranteed to survive a system > > crash thereafter. > > > > Journal creation efficiency is not something you need > > to be concerned about. It's rarely significant as overhead > > in most cases. > > > > For those cases where you might be making large updates > > on a regular basis, it's possible to tell MarkLogic to > > pre-allocate journal space so that it's even more efficient. > > > > On Apr 20, 2012, at 2:23 PM, Danny Sinang wrote: > > > >> Hi Ron, > >> > >> Thanks for the info. > >> > >> So in effect, the journal entries somehow store the actions to be > taken, not the new data to be applied ? > >> > >> I'm asking this to somehow assure myself that journal entry creation > would be fast, even for large transactions. The faster the journal > creation, the less chances of it failing due to an outage. > >> > >> Regards, > >> Danny > >> > >> On Fri, Apr 20, 2012 at 8:58 AM, Ron Hitchens <[email protected]> wrote: > >> > >> No user serviceable parts inside. > >> > >> The journal contains information that describes > >> sets of updates done by transactions. In case of a > >> crash, the journal can be replayed to re-apply any > >> updates that may not yet have been written to the > >> on-disk forests. > >> > >> A transaction does not complete until the journal > >> entry is written to disk, but the corresponding updates > >> to the forest(s) are written later. The database view > >> your queries see are the sum of the on-disk in in-memory > >> stands that comprise forests which make up a database. > >> > >> Journal entries are in a compact binary format that > >> is only used internally by the server to assure data > >> consistency. > >> > >> On Apr 20, 2012, at 1:43 PM, Danny Sinang wrote: > >> > >>> Hi, > >>> > >>> I'm told that for document inserts and updates, an ML journal entry > gets written. > >>> > >>> Does anyone know what gets written to the journal ? Is it just the > xquery getting executed ? Or is it the new data to be appended to the > database ? > >>> > >>> Regards, > >>> Danny > >>> > >>> _______________________________________________ > >>> General mailing list > >>> [email protected] > >>> http://developer.marklogic.com/mailman/listinfo/general > >> > >> --- > >> Ron Hitchens {mailto:[email protected]} Ronsoft Technologies > >> +44 7879 358 212 (voice) http://www.ronsoft.com > >> +1 707 924 3878 (fax) Bit Twiddling At Its Finest > >> "No amount of belief establishes any fact." -Unknown > >> > >> > >> > >> > >> _______________________________________________ > >> General mailing list > >> [email protected] > >> http://developer.marklogic.com/mailman/listinfo/general > >> > >> _______________________________________________ > >> General mailing list > >> [email protected] > >> http://developer.marklogic.com/mailman/listinfo/general > > > > --- > > Ron Hitchens {mailto:[email protected]} Ronsoft Technologies > > +44 7879 358 212 (voice) http://www.ronsoft.com > > +1 707 924 3878 (fax) Bit Twiddling At Its Finest > > "No amount of belief establishes any fact." -Unknown > > > > > > > > > > _______________________________________________ > > General mailing list > > [email protected] > > http://developer.marklogic.com/mailman/listinfo/general > > > > _______________________________________________ > General mailing list > [email protected] > http://developer.marklogic.com/mailman/listinfo/general >
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