MySQL Bugs: #83346: CLIENT_DEPRECATE_EOF not respected when query cache is enabled

Bug #83346	CLIENT_DEPRECATE_EOF not respected when query cache is enabled
Submitted:	12 Oct 2016 17:48	Modified:	7 Jul 2017 9:09
Reporter:	Filipe Silva	Email Updates:
Status:	Won't fix	Impact on me:	None
Category:	MySQL Server: Query Cache	Severity:	S2 (Serious)
Version:	5.7.15	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Results from a cached query are always returned in the same protocol  CLIENT_DEPRECATE_EOF mode as of first execution, no matter what the client says afterwards.

This relates to Bug#83304.

How to repeat:
1. Turn query cache on
2. Create a simple table with one field.
3. Execute the query using a client with  CLIENT_DEPRECATE_EOF turned off.
4. Execute the query using a client with  CLIENT_DEPRECATE_EOF turned on.

Steps 3. and 4. can be executed with Connector/J 5.1.38 and Connector/J 5.1.39 respectively.

Between steps 3. and 4. the response from the server is exactly the same but the first should contain the deprecated EOF packets while the latter the new OK packets form.

Individually, each mode works well, this problem arises when combining clients with the two modes.

Suggested fix:
Make the response from cached queries comply with the CLIENT_DEPRECATE_EOF mode from current session instead of the one from first execution.

Or, invalidate query cache if current CLIENT_DEPRECATE_EOF mode is not the same as per first execution.

Thank you for the report.

Marking Bug #85551 as a duplicate

MySQL will no longer invest in the query cache, see:

http://mysqlserverteam.com/mysql-8-0-retiring-support-for-the-query-cache/

The referenced article from the MySQL Server Blog states that the query cache will continue to be supported for the life time of MySQL 5.7