MySQL Bugs: #97757: NullPointerException with cacheResultSetMetadata=true and executeQuery of "set"

Bug #97757	NullPointerException with cacheResultSetMetadata=true and executeQuery of "set"
Submitted:	24 Nov 2019 6:34	Modified:	27 Mar 18:27
Reporter:	Edmon Luan	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / J	Severity:	S3 (Non-critical)
Version:	8.0.18	OS:	Debian
Assigned to:		CPU Architecture:	x86

Description:
MySQL Server version: 10.3.18-MariaDB-0+deb10u1 Debian 10

Java:
openjdk version "1.8.0_222"
OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_222-b10)
OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.222-b10, mixed mode)

With cacheResultSetMetadata=true, calling Statement.executeQuery("set ...") throws NullPointerException. The set statement can be anything like "set autocommit=0" for example.

With cacheResultSetMetadata=false, Statement.executeQuery("set ...") returns a ResultSet normally.

How to repeat:
Run the following:

Connection c = DriverManager.getConnection(
  "jdbc:mysql://localhost:3306/mysql?sslMode=DISABLED&cacheResultSetMetadata=true&user=..."
);
Statement s = c.createStatement();
s.executeQuery("set autocommit = 0"); // throws NullPointerException

Suggested fix:
Statement.executeQuery("set ...") should behave consistently no matter of cacheResultSetMetadata

Simplified reproduction

Attachment: MySQLCJ8Issue.java (text/x-java), 726 bytes.

stack trace

Attachment: trace (application/octet-stream, text), 594 bytes.

Hello Edmon Luan,

Thank you for the report and test case.

regards,
Umesh

Posted by developer:
 
Added the following entry to the C/J 8.0.20 changelog: 

"A NullPointerException was returned when the connection had cacheResultSetMetadata=true and a query containing any set statements was executed. This fix corrects the issue by adding the missing variable assignment, and also a null check."