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From nitin padalia <padalia.ni...@gmail.com>
Subject Re: [Merging data from memtables and 1 sstables] takes too much time.
Date Wed, 24 Dec 2014 11:32:39 GMT
Is merging costly operation with wide rows?
On Dec 10, 2014 5:53 PM, "nitin padalia" <padalia.nitin@gmail.com> wrote:

> I am using a schema like below:
>
> CREATE TABLE user_location_map (
>     store_id uuid,
>     location_id uuid,
>     user_serial_number text,
>     userobjectid uuid,
>     PRIMARY KEY ((store_id, location_id), user_serial_number)
> ) WITH CLUSTERING ORDER BY (user_serial_number ASC)
>     AND bloom_filter_fp_chance = 0.01
>     AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
>     AND comment = ''
>     AND compaction = {'min_threshold': '4', 'class':
> 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy',
> 'max_threshold': '32'}
>     AND compression = {'sstable_compression':
> 'org.apache.cassandra.io.compress.LZ4Compressor'}
>     AND dclocal_read_repair_chance = 0.1
>     AND default_time_to_live = 0
>     AND gc_grace_seconds = 864000
>     AND max_index_interval = 2048
>     AND memtable_flush_period_in_ms = 0
>     AND min_index_interval = 128
>     AND read_repair_chance = 0.0
>     AND speculative_retry = '99.0PERCENTILE';
>
> Where I run a query like:
> select * from  user_location_map where store_id =
> 17b73358-79e6-11e4-bfd4-0050568aa211 and location_id =
> 2c269ea4-dbfd-32dd-9bd7-a5c22677d18b and user_serial_number =
> 'uI2201';
>
> some times queries like above complete in 3-4 milliseconds, however
> few times they take around 80-90 milliseconds. The data is around 1
> million distributed in 5 nodes with RF 3.
>
> Tacing shows every time most time is consumed by:
> Merging data from memtables and 1 sstables
>
> What could the reason that some times this take too long, however rest
> of the time its fast.
>

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