fuggy_yama created CASSANDRA-9074:
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Summary: Hadoop Cassandra CqlInputFormat pagination - not reading
all input rows
Key: CASSANDRA-9074
URL: https://issues.apache.org/jira/browse/CASSANDRA-9074
Project: Cassandra
Issue Type: Bug
Components: Hadoop
Environment: Cassandra 2.0.11, Hadoop 1.0.4, Datastax java
cassandra-driver-core 2.1.4
Reporter: fuggy_yama
Priority: Minor
I have a 7-node Cassandra (v2.0.11) cluster and a table with 10k rows. I run a
hadoop job (datanodes reside on cassandra nodes of course) that reads data from
that table and I see that only 7k rows is read to map phase.
I checked CqlInputFormat source code and noticed that a CQL query is build to
select node-local date and also LIMIT clause is added (1k default). So that 7k
read rows can be explained:
7 nodes * 1k limit = 7k rows read total
The limit can be changed using CqlConfigHelper:
CqlConfigHelper.setInputCQLPageRowSize(job.getConfiguration(), "1000");
Please help me with questions below:
Is this a desired behavior?
Why CqlInputFormat does not page through the rest of rows?
Is it a bug or should I just increase the InputCQLPageRowSize value?
What if I want to read all data in table and do not know the row count?
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