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[Jdbm-developer] Formal method for evaluation of MVCC algorithms
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From: Kevin D. <ke...@tr...> - 2006-03-04 06:34:31
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<DIV><FONT face=Arial>Bryan-</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>I thought the following
might be interesting to you (or at least
help you get to sleep):</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV></DIV>
<DIV><FONT face=Arial></FONT></DIV>
<DIV><FONT face=Arial><A href="http://www.sai.msu.su/~megera/postgres/gist/papers/concurrency/p465-bernstein.pdf">http://www.sai.msu.su/~megera/postgres/gist/papers/concurrency/p465-bernstein.pdf</A></FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Of particular interest
is the concept of one-copy serializability,
and that this can be proved by showing that
the dependency graph of transactions involved
in an MV transaction log can form an acyclic
graph.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>There are a couple
of algorithms proposed, one of which makes
a direct reference to using 2PL for update
queries and time/transaction stamp resolution
for read-only transactions.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>hmmm - maybe it would
be possible to promote a read-only transaction
to a writable transaction? jdbm2 would
apply the locking logic as if all of the
reads to date were performed at that instant
(but with 2PL enabled). If any of the
records read so far are not valid, the transaction
aborts immediately and can be re-executed
as a writable transaction from the get-go...
That would at least save the hassle of instantiating
all of the objects, etc... unless an abort
was really necessary...</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Certainly, that's a
refinement for the back-burner, but I wanted
to toss it out as it occured to me.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>- K</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Kevin Day<BR>Trumpet,
Inc.<BR><A href="http://www.trumpetinc.com"><FONT
color=#0000ff>www.trumpetinc.com</FONT></A><BR><A
href="mailto:ke...@tr..."><FONT
color=#0000ff>ke...@tr...</FONT></A><BR>602-438-7030</FONT></DIV>
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