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From Edward Capriolo <edlinuxg...@gmail.com>
Subject a plea not to remove rowsize warning
Date Wed, 11 Aug 2010 23:11:26 GMT
Hello all,

I recently posted on list about a situation where two of my nodes from
my 16 node were garbage collecting and at ooming. I was able to move
my xmx from 9gb to 11gb to see that rather then my memory saw tooth. I
would saw tooth around 4 gb before memory shot up like a rocket.

After digging around I noticed the jmx row stats on that node said
maxrowcompacted size = 128 mb. While the mean row size was 2000 byes.

At the time I was unaware of the setting that warns of large rows.
During compaction. Unfortunately this setting is too high by default.
512 mb, since I have been using rowcache.

When something get this key extreme memory pressure is put on the
system to get it in and out of row cache.

I wa able to lower this setting to 10 mb and a got printed nice
warnings showing me the offending keys. I do not know how this got
their. My guess is  null is getting encoded into this key and this key
becomes the graveyard for bad data.

Until the rowcache can handle the large keys better I find it
imperitive to keep the setting and the warnings. As making a program
to range scan all the data to find one big. Key is very intensive.

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