Hi, Thanks Brain and Andy. Got it.
Regards, Aayush. On Thu, Jan 13, 2022, 3:34 PM Andy Seaborne <a...@apache.org> wrote: > > > On 13/01/2022 06:33, Aayush Yadav wrote: > > Hi, > > > > I just had a query regarding how JENA handles deleted nodes in TDB2? I > read > > in the documentation and even saw while implementing, that the nodes that > > are deleted are not removed from storage until compact is run. So how are > > these nodes handled exactly? By handled I mean, how does compact know > which > > nodes to delete from storage, and how does running select all skip these > > triples? > > > > Any insights on this or if anyone could point to which file in the Jena > > code too look into, might help. > > > > Thanks, > > Aayush. > > > > Triples/quads become unreachable from the current roots of the indexes. > > The only nodes to keep are these accessible from triples that are > reachable from the current roots. > > Compact performed by copying the current view of the database and > (optionally) throwing away the old one. > > The copy is of the current state of the database. If a node isn't > reached when copying, it isn't in the new node table. (Same for > triples/quads.) > > There is no reference counting of nodes - too expensive and not simple > because of transactions having different views of the database and may > abort, not commit. > > In TDB2, there are subdirectories "Data-0001" etc The highest number > Data* sub-directory is the active one. The rest are no longer used - you > can zip+moved them elsewhere as a record of the database at a point in > time or just delete them. > > Andy > > > >
