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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-11566) read time out when do count(*)
Date Wed, 13 Apr 2016 19:06:25 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-11566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15239857#comment-15239857
] 

Tyler Hobbs commented on CASSANDRA-11566:
-----------------------------------------

Using {{LIMIT 1}} with {{SELECT count\(*\)}} doesn't limit Cassandra to only counting one
row -- it will still count all rows.  The {{LIMIT}} applies to the number of returned rows,
not the number of processed rows.

> read time out when do count(*)
> ------------------------------
>
>                 Key: CASSANDRA-11566
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11566
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: staging
>            Reporter: nizar
>             Fix For: 3.3
>
>
> Hello I using Cassandra Datastax 3.3, I keep getting read time out even if I set the
limit to 1, it would make sense if the limit is high number .. However only limit 1 and still
timing out sounds odd?
> [cqlsh 5.0.1 | Cassandra 3.3 | CQL spec 3.4.0 | Native protocol v4]
> cqlsh:test> select count(*) from test.my_view where s_id=? and flag=false limit 1;
> OperationTimedOut: errors={}, last_host=
> my key look like this :
> CREATE MATERIALIZED VIEW test.my_view AS
>   SELECT *
>   FROM table_name
>   WHERE id IS NOT NULL AND processed IS NOT NULL AND time IS  NOT NULL AND id IS NOT
NULL
>   PRIMARY KEY ( ( s_id, flag ), time, id )
>   WITH CLUSTERING ORDER BY ( time ASC );
>  I have 5 nodes with replica 3
> CREATE KEYSPACE test WITH replication = {'class': 'NetworkTopologyStrategy', 'dc': '3'}
 AND durable_writes = true;
> Below was the result for nodetoolcfstats
> Keyspace: test
> Read Count: 128770
> Read Latency: 1.42208769123243 ms.
> Write Count: 0
> Write Latency: NaN ms.
> Pending Flushes: 0
> Table: tableName
> SSTable count: 3
> Space used (live): 280777032
> Space used (total): 280777032
> Space used by snapshots (total): 0
> Off heap memory used (total): 2850227
> SSTable Compression Ratio: 0.24706731995327527
> Number of keys (estimate): 1277211
> Memtable cell count: 0
> Memtable data size: 0
> Memtable off heap memory used: 0
> Memtable switch count: 0
> Local read count: 3
> Local read latency: 0.396 ms
> Local write count: 0
> Local write latency: NaN ms
> Pending flushes: 0
> Bloom filter false positives: 0
> Bloom filter false ratio: 0.00000
> Bloom filter space used: 1589848
> Bloom filter off heap memory used: 1589824
> Index summary off heap memory used: 1195691
> Compression metadata off heap memory used: 64712
> Compacted partition minimum bytes: 311
> Compacted partition maximum bytes: 535
> Compacted partition mean bytes: 458
> Average live cells per slice (last five minutes): 102.92671205446536
> Maximum live cells per slice (last five minutes): 103
> Average tombstones per slice (last five minutes): 1.0
> Maximum tombstones per slice (last five minutes): 1
> Table: my_view
> SSTable count: 4
> Space used (live): 126114270
> Space used (total): 126114270
> Space used by snapshots (total): 0
> Off heap memory used (total): 91588
> SSTable Compression Ratio: 0.1652453778228639
> Number of keys (estimate): 8
> Memtable cell count: 0
> Memtable data size: 0
> Memtable off heap memory used: 0
> Memtable switch count: 0
> Local read count: 128767
> Local read latency: 1.590 ms
> Local write count: 0
> Local write latency: NaN ms
> Pending flushes: 0
> Bloom filter false positives: 0
> Bloom filter false ratio: 0.00000
> Bloom filter space used: 96
> Bloom filter off heap memory used: 64
> Index summary off heap memory used: 140
> Compression metadata off heap memory used: 91384
> Compacted partition minimum bytes: 3974
> Compacted partition maximum bytes: 386857368
> Compacted partition mean bytes: 26034715
> Average live cells per slice (last five minutes): 102.99462595230145
> Maximum live cells per slice (last five minutes): 103
> Average tombstones per slice (last five minutes): 1.0
> Maximum tombstones per slice (last five minutes): 1
> Thank you.
> Nizar



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