[CASSANDRA-15435] SELECT JSON does not return the correct value for empty blobs

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 2.2.16, 3.0.20, 3.11.6, 4.0, 4.0-alpha3
• Component/s: CQL/Interpreter
• Bug Category: Correctness
• Severity: Low
• Complexity: Low Hanging Fruit
• Discovered By: User Report
• Platform: All
• Since Version: 2.2.11

Source Control Link

https://github.com/apache/cassandra/commit/c3dc6eb57ef94ca1ff19ab766fc3cc5179242cac

Test and Documentation Plan

Unit tests

• Assignee: Ekaterina Dimitrova
• Reporter: Benjamin Lerer

Authors

Ekaterina Dimitrova

Reviewers

Benjamin Lerer

• Created: 21/Nov/19 12:24
• Updated: 15/May/20 08:39
• Resolved: 09/Dec/19 10:08

Description

In an attempt to fix the side effect of a problem CASSANDRA-13868 was committed in 2.2.11, 3.0.15, 3.11.1 and trunk.
This patch introduced an issue on how empty values were rendered by SELECT JSON queries.
Instead of returning the correct value for the type a null value was now returned.
A user detected that problem for text column and opened CASSANDRA-14245 to request a fix for that problem. Unfortunately, I misunderstood the problem and the fix did not solve the real problem. It only made the code return 'an empty string instead of null values.

The proper fix is to rollback the changes made for CASSANDRA-13868 and CASSANDRA-14245.
Some unit tests also need to be added to test the behavior.