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https://issues.apache.org/jira/browse/DERBY-3823?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13124427#comment-13124427
]
Mamta A. Satoor commented on DERBY-3823:
----------------------------------------
Dag, I wrote a program to see what happens to the resultset's metadata
description when it gets changed underneath while a resultset is still open. (I
ran this program with the current trunk codeline, ie without Dag;s suggested
changes)
As you suspected, embedded version throws an error because the resultset is
still open but netwrok server goes ahead and allows the metadata change but
this change does not get reflected in the resultset's metadata descriptor even
after a fresh fetch of resultset's metadata descriptor after the metadata
change.
To run in the embedded mode, run the program with no parameters or with '1'. To
run it in network server mode, have the network server running and then run the
program with any value other than '1' for the parameter. eg
embedded mode
java DERBY3824StressTestNPE 1
or
java DERBY3824StressTestNPE
For Network server mode
java DERBY3824StressTestNPE 0
The test results for embedded mode looks as follows
*************
Done loading data
char column length is 5
should get error for inserting too large of a data
Error is A truncation error was encountered trying to shrink VARCHAR
'12345678'to length 5.
Exception in thread "main" java.sql.SQLException: Operation 'ALTER TABLE'
cannot be performed on object 'T1' because there is an open ResultSet dependent
on tha
t object.
*************
The test results for network server mode looks as follows
*************
Done loading data
char column length is 5
should get error for inserting too large of a data
Error is A truncation error was encountered trying to shrink VARCHAR
'12345678'to length 5.
char column length after alter table is 5
was able to insert large data
*************
Following is the program.
import java.sql.*;
public class DERBY3824StressTestNPE extends Thread {
public static void main(String[] args) throws Exception {
Connection conn = null;
if (args.length == 1) {
int embedded = Integer.parseInt(args[0]);
if (embedded == 1) {
Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
conn = DriverManager.getConnection(
"jdbc:derby:DERBY4437DB;create=true");
} else {
Class.forName("org.apache.derby.jdbc.ClientDriver");
String url =
"jdbc:derby://localhost:1527/DERBY4437DB;create=true";
conn = DriverManager.getConnection(url);
}
} else {
Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
conn = DriverManager.getConnection(
"jdbc:derby:DERBY4437DB;create=true");
}
conn.setAutoCommit(false);
Statement st = conn.createStatement();
st.executeUpdate("create table t1(c11 int, "+
"c12 varchar(5))");
PreparedStatement ps =
conn.prepareStatement("insert into t1 values(?,'aaaaa')");
for (int i = 0; i < 1000; i++) {
ps.setInt(1, i);
ps.executeUpdate();
}
System.out.println("Done loading data");
conn.commit();
ResultSet rs = st.executeQuery("select * from t1");
for (int i = 0; i < 100; i++) {
rs.next();
}
ResultSetMetaData rsmd = rs.getMetaData();
int charLength = rsmd.getColumnDisplaySize(2);
System.out.println("char column length is " + charLength);
Statement st2 = conn.createStatement();
try {
st2.executeUpdate("insert into t1 values(99,'12345678')");
} catch(Exception ex) {
System.out.println("should get error for inserting too large of
a data");
System.out.println("Error is " + ex.getMessage());
}
st2.execute("alter table t1 alter column c12 set data type
varchar(8)");
rsmd = rs.getMetaData();
charLength = rsmd.getColumnDisplaySize(2);
System.out.println("char column length after alter table is " +
charLength);
st2.executeUpdate("insert into t1 values(99,'12345678')");
System.out.println("was able to insert large data");
}
}
> NullPointerException in stress.multi test
> -----------------------------------------
>
> Key: DERBY-3823
> URL: https://issues.apache.org/jira/browse/DERBY-3823
> Project: Derby
> Issue Type: Bug
> Components: Network Server
> Affects Versions: 10.3.3.1, 10.7.1.1, 10.8.1.2
> Reporter: Kathey Marsden
> Labels: derby_triage10_5_2
> Attachments: d3823-1.diff, derby.log
>
>
> I saw the following NPE in stress.multi running on 10.3 with derbyclient.
> java.lang.NullPointerException
> at
> org.apache.derby.impl.jdbc.EmbedPreparedStatement.getMetaData(Unknown
> Source)
> at org.apache.derby.impl.drda.DRDAConnThread.writeSQLDARD(Unknown
> Source
> )
> at org.apache.derby.impl.drda.DRDAConnThread.processCommands(Unknown
> Sou
> rce)
> at org.apache.derby.impl.drda.DRDAConnThread.run(Unknown Source)
> Cleanup action completed
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