MySQL Bugs: #96059: Error streaming multi resultsets with mysql-connector-java 8.0.x

Bug #96059	Error streaming multi resultsets with mysql-connector-java 8.0.x
Submitted:	2 Jul 2019 8:50	Modified:	7 Jan 2020 18:07
Reporter:	E A	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / J	Severity:	S2 (Serious)
Version:	8.0.16	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	multi resultsets, Streaming

Description:
As we know, people generally use streaming result for large resultsets.
And if there are multi resultsets which are all quite large, we just stream them all. 

However, following code runs totally fine on mysql-connector-java 5.x but just not good on 8.0.x

How to repeat:
See code below:
```
try {
    Connection conn = DriverManager.getConnection(url, user, pass);

    PreparedStatement stmt = conn.prepareStatement(sql, ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
    
    ResultSet rs = null;

    stmt.setFetchSize(Integer.MIN_VALUE);

    stmt.setFetchDirection(ResultSet.FETCH_REVERSE);

    boolean hasResult = stmt.execute();

    while(hasResult) {
        rs = stmt.getResultSet();
        System.out.println("===result set===");
        while (rs.next()) {
            System.out.print("---record---");
            System.out.println(rs.getInt(1));
        }
        hasResult = stmt.getMoreResults();
    }

} catch (Exception e) {
    e.printStackTrace();
}
```
It's good to go on mysql-connector-java 5.x, but throw exceptions on 8.0.x

Suggested fix:
some bugs in `ClientPreparedStatement.getMoreResults()` of 8.0.x

Hello CHAO AI,

Thank you for the report.

regards,
Umesh

Any news?

Any news?

Any news?

Any news?

Hello, 

I am currently experiencing this error while trying to stream results from a stored procedure while using DataGrip 2019.3. Thank you.

Posted by developer:
 
Added the following entry to the Connector/J 8.0.19 changelog:

"Streaming of multiple result sets failed with an error. It was due to an error in switching the streamer source from one result set to another, and this fix corrects the issue"