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From Marcus Eriksson <krum...@gmail.com>
Subject Re: Worse perf after Row Caching version 1.2.5:
Date Thu, 13 Feb 2014 06:32:58 GMT
"select * from <table>" will not populate row cache, but if the row is
cached, it will be used. You need to use "select * from table where X=Y" to
populate row cache.

when setting caching = "rows_only" you disable key cache which might hurt
your performance.


On Wed, Feb 12, 2014 at 9:05 PM, PARASHAR, BHASKARJYA JAY <bp134r@att.com>wrote:

>  Thanks Jonathan,
>
>
>
> I have the cfstats but our prod team has changed some configs after my
> post and I do not have the cfhistograms  information now.
>
>
>
> No Of nodes: 3
>
> Ram: 472GB
>
> Cassandra version: 1.2.5
>
>
>
> I am pasting the cfstats below.
>
>
>
> Regards
>
> Jay
>
>
>
> CREATE TABLE "EnablerCreditReasonInfo" (
>
>   key text PRIMARY KEY,
>
>   "creditReasonDescription" text
>
> ) WITH COMPACT STORAGE AND
>
>   bloom_filter_fp_chance=0.010000 AND
>
>   caching='ROWS_ONLY' AND
>
>   comment='' AND
>
>   dclocal_read_repair_chance=0.000000 AND
>
>   gc_grace_seconds=864000 AND
>
>   read_repair_chance=0.100000 AND
>
>   replicate_on_write='true' AND
>
>   populate_io_cache_on_flush='false' AND
>
>   compaction={'class': 'SizeTieredCompactionStrategy'} AND
>
>   compression={'sstable_compression': 'SnappyCompressor'};
>
>
>
>
>
> CFStats
>
>   Column Family: EnablerCreditReasonInfo
>
>   SSTable count: 3
>
>   Space used (live): 108067
>
>   Space used (total): 108067
>
>   Number of Keys (estimate): 1920
>
>   Memtable Columns Count: 0
>
>   Memtable Data Size: 0
>
>   Memtable Switch Count: 0
>
>   Read Count: 0
>
>   Read Latency: NaN ms.
>
>   Write Count: 0
>
>   Write Latency: NaN ms.
>
>   Pending Tasks: 0
>
>   Bloom Filter False Positives: 0
>
>   Bloom Filter False Ratio: 0.00000
>
>   Bloom Filter Space Used: 2232
>
>   Compacted row minimum size: 61
>
>   Compacted row maximum size: 149
>
>   Compacted row mean size: 100
>
>
>
> *From:* Jonathan Lacefield [mailto:jlacefield@datastax.com]
> *Sent:* Tuesday, February 11, 2014 10:43 AM
> *To:* user@cassandra.apache.org
> *Subject:* Re: Worse perf after Row Caching version 1.2.5:
>
>
>
> Hello,
>
>
>
>   Please paste the output of cfhistograms for these tables.  Also, what
> does your environment look like, number of nodes, disk drive configs,
> memory, C* version, etc.
>
>
>
> Thanks,
>
>
>
> Jonathan
>
>
>   Jonathan Lacefield
>
> Solutions Architect, DataStax
>
> (404) 822 3487
>
> [image: Image removed by sender.] <http://www.linkedin.com/in/jlacefield>
>
>
>
>
>
> [image: Image removed by sender.]<http://www.datastax.com/what-we-offer/products-services/training/virtual-training>
>
>
>
> On Tue, Feb 11, 2014 at 10:26 AM, PARASHAR, BHASKARJYA JAY <bp134r@att.com>
> wrote:
>
> Hi,
>
>
>
> I have two tables and I enabled row caching for both of them using CQL.
> These two CF's are very small with one about 300 rows and other < 2000
> rows. The rows themselves are small.
>
> Cassandra heap: 8gb.
>
> a.       alter table TABLE_X with caching = 'rows_only';
>
> b.      alter table TABLE_Y with caching = 'rows_only';
>
> I also changed row_cache_size_in_mb: 1024 in the Cassandra.yaml file.
>
> After extensive testing, it seems the performance of Table_X degraded from
> 600ms to 750ms and Table_Y gained about 10 ms (from 188ms to 177 ms).
>
> More Info
>
> Table X is always queried with "Select * from Table_X";  Cfstats in
> Table_X shows Read Latency: NaN ms. I assumed that since we select all the
> rows, the entire table would be cached.
>
> Table_Y has a secondary index and is queried on that index.
>
>
>
>
>
> Would appreciate any input why the performance is worse and how to enable
> row caching for these two tables.
>
>
>
> Thanks
>
> Jay
>
>
>
>
>
>
>

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