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From "Raymond Raymond" <raymond_de...@hotmail.com>
Subject Is there any means to get the size of a log record?
Date Tue, 28 Feb 2006 21:31:11 GMT
I am trying to do some statistics to estimate recovery speed.
I can get how many log records the recovery process scaned
during the recovery and how long the recovery takes.The recovery
speed I got so far is something like

X log records/second

But, to use the recovery speed to schedule the checkpoint,
I need it likes

X KB/second

I looked into the org.apache.derby.impl.store.raw.log.LogToFile.java .
The checkpoint is trigger in the flush(long fileNumber, long wherePosition)
function. The condition to trigger a checkpoint is :

if ((logWrittenFromLastCheckPoint + potentialLastFlush) > checkpointInterval 
&&
?checkpointDaemon != null && !checkpointDaemonCalled && !inLogSwitch)

logWrittenFromLastCheckPoint, potentialLastFlush and?checkpointInterval
are in size (X bytes), so, I need the revovery speed in size (e.g. X 
KB/second).
In another word, I want to know how much (KB) log the recovery process
scaned during recovery. I refered to
http://db.apache.org/derby/papers/logformats.html,
it says the log record wrapper keeps the length of the log record.
I checked the source code and found the length of the log record
is only used in the getNextRecordBackward() and getNextRecordForward()
functions in org.apache.derby.impl.store.raw.log.Scan.java. I can't
get it outside those functions. Anyone can give me some suggestions to
solve the problem?

Thanks.


Raymond

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