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From "B. Todd Burruss" <bburr...@real.com>
Subject get_slice slow
Date Wed, 25 Aug 2010 04:14:44 GMT
i am using get_slice to pull columns from a row to emulate a queue.  
column names are TimeUUID and the values are small, < 32 bytes.  simple 
ColumnFamily.

i am using SlicePredicate like this to pull the first ("oldest") column 
in the row:

         SlicePredicate predicate = new SlicePredicate();
         predicate.setSlice_range(new SliceRange(new byte[] {}, new 
byte[] {}, false, 1));

         get_slice(rowKey, colParent, predicate, QUORUM);

once i get the column i remove it.  so there are a lot of gets and 
mutates, leaving lots of deleted columns.

get_slice starts off performing just fine, but then falls off 
dramatically as the number of columns grows.  at its peak there are 
100,000 columns and get_slice is taking over 100ms to return.

i am running a single instance of cassandra 0.7 on localhost, default 
config.  i've done some googling and can't find any tweaks or tuning 
suggestions specific to get_slice.  i already know about separating 
commitlog and data, watching iostat, GC, etc.

any low hanging tuning fruit anyone can think of?  in 0.6 i recall an 
index for columns, maybe that is what i need?

thx

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