[CASSANDRA-8940] Inconsistent select count and select distinct

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 2.0.16, 2.1.6
• Component/s: Legacy/Local Write-Read Paths

Environment

2.1.2

• Severity: Normal
• Since Version: 2.0.14
• Assignee: Benjamin Lerer
• Reporter: Frens Jan Rumph

Authors

Benjamin Lerer

Reviewers

Aleksey Yeschenko

• Created: 10/Mar/15 16:23
• Updated: 16/Apr/19 09:31
• Resolved: 15/May/15 15:02

Description

When performing select count( * ) from ... I expect the results to be consistent over multiple query executions if the table at hand is not written to / deleted from in the mean time. However, in my set-up it is not. The counts returned vary considerable (several percent). The same holds for select distinct partition-key-columns from ....

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>
);

The table contains around 35k rows (I'm not trying to be funny here ...). The consistency level for the queries was ONE.