thx artie,
i haven't used a super CF because i thought it has more trouble doing
slices because the entire row must be deserialized to get to the
subcolumn you want?
iostat is nothing, 0.0. i have plenty of RAM and the OS is I/O caching
nicely
i haven't used the key cache, because i only have one key, the row of
the queue ;)
i haven't used row cache because i need the row to grow quite large,
millions of columns. and the size of data could be arbitrary - right
now i am testing with < 32 byte values per column.
i do need quorum consistency.
i have read previous that some folks are using a single row with
millions of columns. is anyone using get_slice to pick off the first or
the last column in the row?
On 08/24/2010 09:25 PM, Artie Copeland wrote:
Have you tried using a super column, it seems that having a row with
over 100K columns and growing would be alot for cassandra to
deserialize? what is iostat and jmeter telling you? it would be
interesting to see that data. also what are you using for you key or
row caching? do you need to use a quorum consistency as that can slow
down reads as well, can you use a lower consistency level?
Artie
On Tue, Aug 24, 2010 at 9:14 PM, B. Todd Burruss <bburr...@real.com
<mailto:bburr...@real.com>> wrote:
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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