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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4172) You can open a read-write connection to a database which was originally opened by another thread using the classpath subprotocol
Date Thu, 23 Apr 2009 17:28:30 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12702018#action_12702018

Rick Hillegas commented on DERBY-4172:

How does the following user-visible behavior sound? I think this would be easy to explain
and the backward incompatibilities would be very rare (probably non-existent) and easy to

*  We could distinguish between logical and physical database names:
          o A logical database name consists of the subprotocol plus the database path. That
is, each subprotocol defines a separate namespace of databases.
          o The physical database is an actual database which is opened. The same physical
database may have more than one logical name. 

* We would prevent a physical database from being opened under two different logical names
simultaneously. Once a database has been opened under a logical name, other connections to
the database must use that original logical name. After the database has been closed, it can
be re-opened under a different logical name. 

> 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:
>            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
> 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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