Thanks for the pointers Paolo. Now subscribed to [email protected]
On 25 February 2011 09:17, Paolo Castagna <[email protected]>wrote: > > > Hi Danny, > Dave and Damian have already answered your question. > In the past, I had those sort of doubts about MRSW myself. > A simple multi threaded test can help finding the answer. > > For clarity, it's MR XOR SW. > > It's an exclusive OR: if you are writing, nobody can read. > Therefore a long write would block access to readers. > Similarly, a long read would block any write too. > > There is an issue (i.e. New Feature) for this: > https://issues.apache.org/jira/browse/JENA-41 > We should discuss technical details there. > > Andy proposed "journaled file access". > > I'd like to help on this and try to do a prototype as a proof of concept. > However, I am not an expert on this (i.e. I've never wrote a journaled > file access system before) and it does not appear to be only a "small > matter of programming". ;-) > > There are a lot of details which are not clear to me. > > Damian's suggestion works perfectly for your. > > Paolo > > PS: > I know it's a pain, but we are trying to move the mailing > list to Apache. Please, subscribe by sending an email to: > jena-dev-subscribe AT incubator.apache.org > jena-users-subscribe AT incubator.apache.org > > > Danny Ayers wrote: > > on the wiki it says: > > [[ > > TDB provides a Multiple Reader or Single Writer (MRSW) policy for > > concurrency access. Applications are expected to adhere to this policy > > - it is not automatically checked. > > > > One gotcha is Java iterators. An iterator that is moving over the > > database is making read operations and no updates to the dataset are > > possible while an iterator is being used. > > ]] > > > > I'd like to check I'm reading this correctly - is it that many readers > > can access the data concurrently but the (one and only) writer should > > have an exclusive lock - and that lock should block reading..? > > > > The scenario I'm looking at will be TDB shared between Fuseki and > > programmatic access (a Turtle editor). > > > > I've haven't yet really got a clue how I'll handle the sharing, so if > > anyone's got any code for a similar situation I'd be grateful for a > > pointer. > > > > (Right now I've got the editing happening on a single memory model, so > > for the moment at least I can probably get away with access to TDB > > models through a read-(edit)-replace kind of cycle). > > > > Cheers, > > Danny. > > > __._,_.___ > Reply to > sender<[email protected]?subject=Re%3A%20%5Bjena-dev%5D%20TDB%20concurrency>| > Reply > to > group<[email protected]?subject=Re%3A%20%5Bjena-dev%5D%20TDB%20concurrency>| > Reply > via web > post<http://groups.yahoo.com/group/jena-dev/post;_ylc=X3oDMTJxcDRqbnVxBF9TAzk3MzU5NzE0BGdycElkAzM5OTc1NTMEZ3Jwc3BJZAMxNzA1MDA3MTgxBG1zZ0lkAzQ2ODcxBHNlYwNmdHIEc2xrA3JwbHkEc3RpbWUDMTI5ODYyMTg3NQ--?act=reply&messageNum=46871>| > Start > a New > Topic<http://groups.yahoo.com/group/jena-dev/post;_ylc=X3oDMTJlbHB2Y3Q2BF9TAzk3MzU5NzE0BGdycElkAzM5OTc1NTMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwNmdHIEc2xrA250cGMEc3RpbWUDMTI5ODYyMTg3NQ--> > Messages in this > topic<http://groups.yahoo.com/group/jena-dev/message/46867;_ylc=X3oDMTM2ZnVnYmhrBF9TAzk3MzU5NzE0BGdycElkAzM5OTc1NTMEZ3Jwc3BJZAMxNzA1MDA3MTgxBG1zZ0lkAzQ2ODcxBHNlYwNmdHIEc2xrA3Z0cGMEc3RpbWUDMTI5ODYyMTg3NQR0cGNJZAM0Njg2Nw-->( > 4) > Recent Activity: > > - New > Members<http://groups.yahoo.com/group/jena-dev/members;_ylc=X3oDMTJmYnRiOWM0BF9TAzk3MzU5NzE0BGdycElkAzM5OTc1NTMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwN2dGwEc2xrA3ZtYnJzBHN0aW1lAzEyOTg2MjE4NzU-?o=6> > 5 > > Visit Your > Group<http://groups.yahoo.com/group/jena-dev;_ylc=X3oDMTJlMWhxY3ZjBF9TAzk3MzU5NzE0BGdycElkAzM5OTc1NTMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwN2dGwEc2xrA3ZnaHAEc3RpbWUDMTI5ODYyMTg3NQ--> > [image: Yahoo! > Groups]<http://groups.yahoo.com/;_ylc=X3oDMTJkcmljbnU5BF9TAzk3MzU5NzE0BGdycElkAzM5OTc1NTMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwNmdHIEc2xrA2dmcARzdGltZQMxMjk4NjIxODc1> > Switch to: > Text-Only<[email protected]?subject=Change+Delivery+Format:+Traditional>, > Daily Digest<[email protected]?subject=Email+Delivery:+Digest>• > Unsubscribe <[email protected]?subject=Unsubscribe> • Terms > of Use <http://docs.yahoo.com/info/terms/> > . > > __,_._,___ > -- http://danny.ayers.name
