incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From aaron morton <aa...@thelastpickle.com>
Subject Re: get_slice on wide rows
Date Tue, 21 Aug 2012 09:46:56 GMT
> Is the problem that cassandra is attempting to load all the deleted columns into memory?

Yup. 

The talk by Mat Dennis at the Cassandra Summit may be of interest to you. He talks about similar
things http://www.datastax.com/events/cassandrasummit2012/presentations

Drop the gc_grace_seconds to 1 so that tombstones can be purged faster. A column level tombstone
still has to hit disk so that it will overwrite any existing column on disk. (so setting gc_grace_seconds
to 0 has pretty much the same effect). 

You may also want to try levelled DB on the CF http://www.datastax.com/dev/blog/when-to-use-leveled-compaction

> Is the solution here partitioning the wide row into multiple narrower rows?
That's also sensible. I would give the approach above a try first, may give you more bang
for your buck. 
 
Cheers
 
-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 21/08/2012, at 4:49 AM, feedly team <feedlydev@gmail.com> wrote:

> I have a column family that I am using for consistency purposes. Basically a marker column
is written to a row in this family before some actions take place and is deleted only after
all the actions complete. The idea is that if something goes horribly wrong this table can
be read to see what needs to be fixed. 
> 
> In my dev environment things worked as planned, but in a larger scale/high traffic environment,
the slice query times out and then cassandra quickly runs out of memory. The main difference
here is that there is a very large number of writes (and deleted columns) in the row my code
is attempting to read. Is the problem that cassandra is attempting to load all the deleted
columns into memory? I did an sstableToJson dump and saw that the "d" deletion marker seemed
to be present for the columns, though i didn't write any code to check all values. Is the
solution here partitioning the wide row into multiple narrower rows?


Mime
View raw message