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From "Rumph, Frens Jan" <m...@frensjan.nl>
Subject Inconsistent count(*) and distinct results from Cassandra
Date Wed, 04 Mar 2015 11:54:36 GMT
Hi,

Is it to be expected that select count(*) from ... and select distinct
partition-key-columns from ... to yield inconsistent results between
executions even though the table at hand isn't written to?

I have a table in a keyspace with replication_factor = 1 which is something
like:

CREATE TABLE tbl (
    id frozen<id_type>,
    bucket bigint,
    offset int,
    value double,
    PRIMARY KEY ((id, bucket), offset)
)

The frozen udt is:

CREATE TYPE id_type (
    tags map<text, text>
);

When I do select count(*) from tbl several times the actual count varies
with 5 to 10%. Also when performing select distinct id, bucket from tbl the
results aren't consistent over several query executions. The table is not
being written to at the time I performed the queries.

Is this to be expected? Or is this a bug? Is there a alternative method /
workaround?

I'm using cqlsh 5.0.1 with Cassandra 2.1.2 on 64bit fedora 21 with Oracle
Java 1.8.0_31.

Thanks in advance,
Frens Jan

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