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https://issues.apache.org/jira/browse/CASSANDRA-11314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15184907#comment-15184907
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Benjamin Lerer commented on CASSANDRA-11314:
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{quote}Because of the fact that we fetch the data on the client side and then
count , this indicates that also the datafetch is flawed because for some
reason we are missing chunks of data , I have not analysed the data just
counted it ...{quote}
It is a good thing. It will help us to dig in the problem.
Based on you results, my guess is that you have 55677 rows in your partition
and that for some reasons some get lost.
{quote}Ideas ? What to look over next ... ?{quote}
I will take over from there and come back to you if I run into some problems. I
will try to have a fix for 3.5.
Thanks for all your efforts :-)
> Inconsistent select count(*)
> ----------------------------
>
> Key: CASSANDRA-11314
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11314
> Project: Cassandra
> Issue Type: Bug
> Components: Local Write-Read Paths
> Environment: Ununtu 14.04 LTS
> Reporter: Mircea Lemnaru
> Assignee: Benjamin Lerer
> Attachments: testrun.log, vnodes_and_hosts
>
>
> Hello,
> I currently have this setup:
> Cassandra 3.3 (Community edition downloaded from Datastax) installed on 3
> nodes and I have created this table:
> CREATE TABLE billing.collected_data_day (
> collection_day int,
> timestamp timestamp,
> record_id uuid,
> dimensions map<text, text>,
> entity_id text,
> measurements map<text, text>,
> source_id text,
> PRIMARY KEY (collection_day, timestamp, record_id)
> ) WITH CLUSTERING ORDER BY (timestamp ASC, record_id ASC)
> AND bloom_filter_fp_chance = 0.01
> AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
> AND comment = ''
> AND compaction = {'class':
> 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy',
> 'max_threshold': '32', 'min_threshold': '4'}
> AND compression = {'chunk_length_in_kb': '64', 'class':
> 'org.apache.cassandra.io.compress.LZ4Compressor'}
> AND crc_check_chance = 1.0
> 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 = '99PERCENTILE';
> This table as you notice is partitioned by collection_day. This is because at
> the end of the day we need to have fast access to all the data generated in a
> day. collection day will be the x day from 1970
> In this table we have inserted roughly 12milion rows for testing purposes and
> we did a simple count. As you can see the results vary ...
> cqlsh:billing> select count(*) from collected_data_day where
> collection_day=16462;
> count
> -------
> 55341
> (1 rows)
> cqlsh:billing> select count(*) from collected_data_day where
> collection_day=16462;
> count
> -------
> 55372
> (1 rows)
> cqlsh:billing> select count(*) from collected_data_day where
> collection_day=16462;
> count
> -------
> 55300
> (1 rows)
> cqlsh:billing> select count(*) from collected_data_day where
> collection_day=16462;
> count
> -------
> 55300
> (1 rows)
> cqlsh:billing> select count(*) from collected_data_day where
> collection_day=16462;
> count
> -------
> 55300
> (1 rows)
> cqlsh:billing> select count(*) from collected_data_day where
> collection_day=16462;
> count
> -------
> 55303
> (1 rows)
> cqlsh:billing> select count(*) from collected_data_day where
> collection_day=16462;
> count
> -------
> 55374
> (1 rows)
> I am running the query from the seed node of the cassandra cluster. As you
> can see most of the results are varying and I don't know the reason for this.
> We are not writing anything into the cluster at this time , we are only
> querying the cluster and only using this CQLSH.
> This is very similar to CASSANDRA-8940 but that is targeted for 2.1x
> Could it be that we are having the same issue in 3.3 ?
> Please let me know what extra info I can provide
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