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https://issues.apache.org/jira/browse/DERBY-4172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12702367#action_12702367
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Knut Anders Hatlen commented on DERBY-4172:
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I think you can see a similar issue with the jar protocol:
jdbc:derby:jar:(mydb.jar)wombat
jdbc:derby:jar:(/export/home/mydb.jar)wombat
To avoid a special rule for the directory subprotocol, perhaps we could say: A
logical database name consists of the subprotocol plus a canonical database
path determined by the subprotocol's persistent service.
The described behaviour sounds fine to me. Basically, what you suggest we
disallow is the following (assuming /path/to is in the classpath):
connect 'jdbc:derby:directory:/path/to/wombat'; -> OK
connect 'jdbc:derby:classpath:wombat'; -> ERROR: The database '/path/to/wombat'
is already opened using another protocol
This would currently work, but the second (read-only) connection could see
strange behaviour if the first connection makes any changes to the database, so
I think disallowing it is fine.
> You can open a read-write connection to a database which was originally
> opened by another thread using the classpath subprotocol
> --------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-4172
> URL: https://issues.apache.org/jira/browse/DERBY-4172
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.6.0.0
> Reporter: Rick Hillegas
>
> The original connection, using the classpath subprotocol, was supposed to
> open the DATABASE (not the connection) as read-only, according to the
> Developer's Guide section titled "Database connection examples". However, I
> am able to write to this database in another connection which opens the
> database using the default, file-based protocol.
> At a minimum, the documentation is wrong. But the documentation may be trying
> to impose a consistent, easily described model on the behavior of our
> subprotocols. It may be that the behavior of our subprotocols cannot be
> described by a simple set of rules that users can grasp easily.
> To show this problem, I created a database and then moved it into a directory
> on my classpath (in this case, trunk/classes). Here is a script which shows
> this behavior:
> connect 'jdbc:derby:classpath:derby10.6' as conn1;
> -- fails because a database which is opened on the classpath is supposed to
> be marked as read-only
> insert into t( a ) values 1;
> connect 'jdbc:derby:trunk/classes/derby10.6' as conn2;
> -- this succeeds even though the database is supposed to be read-only
> -- according to the Developer's Guide section "Database connection examples"
> insert into t( a ) values 2;
> select * from t;
> delete from t;
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