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From "Thibaut (Updated) (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-4137) QUORUM Multiget RangeSliceQuery causes unnecessary writes to read entries
Date Wed, 11 Apr 2012 16:47:20 GMT


Thibaut updated CASSANDRA-4137:

    Priority: Major  (was: Critical)
> QUORUM Multiget RangeSliceQuery causes unnecessary writes to read entries
> -------------------------------------------------------------------------
>                 Key: CASSANDRA-4137
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 0.8.9
>            Reporter: Thibaut
> From the mailing list:
> I created a new test keyspace and added 10 000 keys to it. The cluster has 3 machines,
RF=3, read repair disabled (enabling it didn't change anything). The keyspace doesn't contain
any thumbstones. No keys were deleted.
> When I fetch a rangeslice through hector and set the consistency level to quorum, according
to cfstats (and also to the output files on the hd), cassandra seems to execute a write request
for each read I execute. The write count in cfstats is increased when I execute the rangeslice
function over the same range again and again (without saving anything at all).
> If I set the consistency level to ONE or ALL, no writes are executed.
> I checked the writes on one machine. They increased by 2300 for each iteration over the
10000 keys. I didn't check, but this probably corresponds to the number of keys for which
the machine is responsible.
> Code:
>                                 Keyspace ks = getConnection(cluster, consistencylevel);
> 				RangeSlicesQuery<String, String, V> rangeSlicesQuery = HFactory.createRangeSlicesQuery(ks,
StringSerializer.get(), StringSerializer.get(), s);
> 				rangeSlicesQuery.setColumnFamily(columnFamily);
> 				rangeSlicesQuery.setColumnNames(column);
> 				rangeSlicesQuery.setKeys(start, end);
> 				rangeSlicesQuery.setRowCount(maxrows);
> 				QueryResult<OrderedRows<String, String, V>> result = rangeSlicesQuery.execute();
> 				return result.get();

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