MySQL Bugs: #67318: SQLException thrown on already closed ResultSet

Bug #67318	SQLException thrown on already closed ResultSet
Submitted:	22 Oct 2012 6:11	Modified:	10 Mar 2014 20:27
Reporter:	ANDREY Andrey Radionov	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / J	Severity:	S5 (Performance)
Version:	5.1.21	OS:	Any
Assigned to:	Alexander Soklakov	CPU Architecture:	Any
Tags:	close, ResultSet, SqlException

Description:
Calling ResultSet.close on already closed ResultSet cause SQLException, which silently discarded. There is two issues with that:

1) This heavily affects performance.
2) Violates ResultSet API: "Calling the method close on a ResultSet object that is already closed is a no-op." (http://docs.oracle.com/javase/6/docs/api/java/sql/ResultSet.html#close%28%29)

Here is problem code in com.mysql.jdbc.ResultSetImpl:

		try {
			locallyScopedConn = checkClosed();
		} catch (SQLException sqlEx) {
			return; // already closed
		}

This issue happens in normal-close scenario:
1) close ResultSet
2) close PreparedStatement
3) close Connection (in case of pooling)

Closing PreparedStatement force closing of its ResultSets. But ResultSet was closed in step1, so this generates SQLException in PreparedStatement.close.

How to repeat:
		Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/test", "root", "1");
		PreparedStatement stmt = conn.prepareStatement("select 1 from dual");
		ResultSet rs = stmt.executeQuery();
		rs.close();
		stmt.close(); // here SQLException will be generated and silently discarded

Patch to fix this issue.

Attachment: ResultSetImpl.patch (application/octet-stream, text), 658 bytes.

Andrey is right. We see also this problem. Using an exception to control the flow of the code is not so good idea IMHO.

Hi Andreys,

Thank you for the report.

Verified as described.

Another problem with this change is that the exception is always logged. This is noise in the logfile.

Please fix this behavior since any versions >= 5.1.21 are unusable for us.

Bug#17811638 marked as duplicate of this one.

Bug#70882 marked as duplicate of this one

Bug#71966 marked as duplicate of this one.

This bug is almost 1.5 yrs old. Given that multiple people have provided patches and considering the _significant_ performance impact this has, and especially considering that users are more likely to hit this with Java 7's try-with-resource, I'm apalled that this hasn't been fixed yet.

Can somoone comment on what the blocker(s) are for this to be accepted?

Added the following entry into the Connector/J 5.1.30 changelog:

"Calling ResultSet.close() on an already closed ResultSet caused an SQLException. While the exception was silently discarded, it did result in performance issues. This fix makes Connector/J comply with the Java specification that when a ResultSet object is already closed, application of the close method on it should be a no-op."

Thanks, can't wait for this update! Any ETA for the 5.1.30 release?

Hi Diwaker,

The date isn't defined yet. You could approximate taking into account that we try to do maintenance releases every 2-3 months.

Thanks, Alexander. The last release (5.1.29) was in February although 5.1.27 and 5.1.28 were released within a month of each other. So I'm guessing we should expect an April/May release?