Sylvain Lebresne created CASSANDRA-8272:
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Summary: 2ndary indexes can return stale data
Key: CASSANDRA-8272
URL: https://issues.apache.org/jira/browse/CASSANDRA-8272
Project: Cassandra
Issue Type: Bug
Reporter: Sylvain Lebresne
When replica return 2ndary index results, it's possible for a single replica to
return a stale result and that result will be sent back to the user,
potentially failing the CL contract.
For instance, consider 3 replicas A, B and C, and the following situation:
{noformat}
CREATE TABLE test (k int PRIMARY KEY, v text);
CREATE INDEX ON test(v);
INSERT INTO test(k, v) VALUES (0, 'foo');
{noformat}
with every replica up to date. Now, suppose that the following queries are done
at {{QUORUM}}:
{noformat}
UPDATE test SET v = 'bar' WHERE k = 0;
SELECT * FROM test WHERE v = 'foo';
{noformat}
then, if A and B acknowledge the insert but C respond to the read before having
applied the insert, then the now stale result will be returned (since C will
return it and A or B will return nothing).
A potential solution would be that when we read a tombstone in the index (and
provided we make the index inherit the gcGrace of it's parent CF), instead of
skipping that tombstone, we'd insert in the result a corresponding range
tombstone.
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