Ti copyback with tj reads because ti cant hurt tj but

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: hing Ti writes and Ti ends reading before Tj ends reading v r w v w • 3) Tj reads & writes nothing Ti writes and Ti ends reading before Tj ends reading r r v v w w – Overlap of Ti copyback with Tj reads because Ti can’t hurt Tj, but Tj might hurt Ti if its writes start too soon Simple testing of sets More parallelism • Long critical section if copyback slow • Test clearly preceding (no longer changing) transactions outside critical section Lock Unlock Even more parallelism • Add ordered testing of condition 3 Space issues • What if run out of space for sets? – Abort & retry • What about repeated abort & retry? – Hold critical section in a retry (ugh) Applic to B-trees • Models B-trees with lots of entries in each page (199), uniform key insertion, interior nodes cacheable and leaf pages not cacheable • Does consider splitting a leaf, but apparently not rotating tree to maintain balance (not needed if inserts are uniform :-) • Concludes for such B-trees that conflict, abort and restart will be rare (0.07%) Eval • Thought experiment – Not fair as really a database theory paper then • Analysis of B-tree not appropriate – Really should have modeled rotations as “randomness” is far too unlikely • Very influential: “optimistic methods” is current label of anything trying first then checking if it had a conflict and undoing it Lock-based Concurrency Control Client code BEGIN lookup • U...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online