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https://issues.apache.org/jira/browse/CASSANDRA-11566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15245719#comment-15245719
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Jack Krupansky commented on CASSANDRA-11566:
--------------------------------------------
COUNT(\*) should only be used on relatively small tables or for relatively
narrow token ranges or relatively narrow slices of wide rows - probably no more
than thousands or maybe hundreds of rows and will depend on your data and your
hardware. Your table may have only 8 "keys", but that means 8 partition keys,
not primary keys. Your table is 120 MB, which is not large as tables go, but
may in fact be large enough to fail to complete the count operation in a small
amount of time.
Try doing a count for each of the partition keys in that table. Maybe one of
the rows is very wide and causing performance to bog down.
(FWIW, if you need to write "(\*)" in Jira, you need to escape the \* with a
backslash, as in "(\*)".)
> 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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