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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4313) JDBC.dropUsingDMD() may skip dropping objects
Date Fri, 17 Jul 2009 14:11:15 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12732537#action_12732537

Knut Anders Hatlen commented on DERBY-4313:

I tested this manually by making dropUsingDMD() public and use it to drop these three tables:

        s.execute("create table a(x int)");
        s.execute("create table b(x int primary key)");
        s.execute("create table c(x int references b(x))");

Using the embedded driver, all the tables were dropped after dropUsingDMD() had returned.
Using the client driver, the table B was still there after dropUsingDMD().

The difference seems to be that the embedded driver stops executing the statements in the
batch after the first failure and only returns the status for the succeeding statements, whereas
the client driver continues executing statements after the first failure in the batch. I'll
log a separate issue for the difference between client and embedded in handling errors in
a batch. Only the bug in dropUsingDMD() will be handled in this issue.

> JDBC.dropUsingDMD() may skip dropping objects
> ---------------------------------------------
>                 Key: DERBY-4313
>                 URL: https://issues.apache.org/jira/browse/DERBY-4313
>             Project: Derby
>          Issue Type: Bug
>          Components: Test
>    Affects Versions:
>            Reporter: Knut Anders Hatlen
>            Assignee: Knut Anders Hatlen
>            Priority: Minor
> This loop in JDBC.dropUsingDMD() looks broken:
>         // Remove any statements from the list that succeeded.
> 		boolean didDrop = false;
> 		for (int i = 0; i < results.length; i++)
> 		{
> 			int result = results[i];
> 			if (result == -3 /* Statement.EXECUTE_FAILED*/)
> 				hadError = true;
> 			else if (result == -2/*Statement.SUCCESS_NO_INFO*/)
> 				didDrop = true;
> 			else if (result >= 0)
> 				didDrop = true;
> 			else
> 				Assert.fail("Negative executeBatch status");
>             if (didDrop)
>                 ddl.set(i, null);
> 		}
> It is supposed to check the status of each individual statement executed in a batch,
and clear the successful ones from an ArrayList so that only the unsuccessful ones are left.
> However, if one of the statements is reported to have failed, and one of the proceeding
statements has been successful, the failed statement will be removed from the ArrayList because
didDrop is true. This means that some of the failed statements are not retried later. The
statements normally fail because some other object depends on the object being dropped, and
they usually succeed when they are retried after the other objects have been dropped. By not
retrying, some objects that were supposed to be dropped may be left in the database.

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