[CASSANDRA-12107] Fix range scans for table with live static rows

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.0.9, 3.8
• Component/s: Legacy/CQL
• Severity: Normal
• Assignee: Sharvanath Pathak
• Reporter: Sharvanath Pathak

Authors

Sharvanath Pathak

Reviewers

Benjamin Lerer

• Created: 29/Jun/16 00:37
• Updated: 16/Apr/19 09:30
• Resolved: 14/Jul/16 19:47

Description

We were seeing some weird behaviour with limit based scan queries. In particular, we see the following:

$ cqlsh -k sd -e "consistency local_quorum; SELECT uuid, token(uuid) FROM files WHERE token(uuid) >= token('6b470c3e43ee06d1') limit 2"
Consistency level set to LOCAL_QUORUM.

 uuid             | system.token(uuid)
------------------+----------------------
 6b470c3e43ee06d1 | -9218823070349964862
 484b091ca97803cd | -8954822859271125729

(2 rows)
$ cqlsh -k sd -e "consistency local_quorum; SELECT uuid, token(uuid) FROM files WHERE token(uuid) > token('6b470c3e43ee06d1') limit 1"
Consistency level set to LOCAL_QUORUM.

 uuid             | system.token(uuid)
------------------+----------------------
 c348aaec2f1e4b85 | -9218781105444826588

In the table uuid is partition key, and it has a clustering key as well.
So the uuid "c348aaec2f1e4b85" should be the second one in the limit query. After some investigation, it seems to me like the issue is in the way DataLimits handles static rows. Here is a patch for trunk (https://github.com/sharvanath/cassandra/commit/9a460d40e55bd7e3604d987ed4df5c8c2e03ffdc) which seems to fix it for me. Please take a look, seems like a pretty critical issue to me.

I have forked the dtests for it as well. However, since trunk has some failures already, I'm not fully sure how to infer the results.
http://cassci.datastax.com/view/Dev/view/sharvanath/job/sharvanath-fixScan-dtest/
http://cassci.datastax.com/view/Dev/view/sharvanath/job/sharvanath-fixScan-testall/