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updated lsn-estimation stuff.

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Sears Russell 2006-09-06 00:42:53 +00:00
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doc/paper3/LLADD.tex
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@ -767,6 +767,17 @@ a lower bound for the LSN of each page, rather than reading it from the page.
One possible lower bound is the LSN of the most recent checkpoint. One possible lower bound is the LSN of the most recent checkpoint.
Alternatively, \yad could occasionally store its list of dirty pages Alternatively, \yad could occasionally store its list of dirty pages
and their LSNs to the log (Figure~\ref{fig:lsn-estimation}). and their LSNs to the log (Figure~\ref{fig:lsn-estimation}).
If a page is present in the most recent list of dirty pages we use
the LSN in the list as our estimate. Otherwise, we use the LSN of the
log entry. This is safe because
the page was not updated between the most recent update to the on-disk
version (the ``true'' LSN of the page), and the point at which the
list was written to log. Therefore, each dirty list is an
accurate sparse representation of the LSNs of the entire page file. The
buffer pool must maintain this information whether or not LSN-free
pages are in use, so we expect the runtime overhead to be minimal.
\begin{figure} \begin{figure}
\includegraphics[% \includegraphics[%
viewport=0bp 0bp 460bp 225bp, viewport=0bp 0bp 460bp 225bp,

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doc/paper3/figs/lsn-estimation.pdf
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