Derby
  1. Derby
  2. DERBY-4590

You can drop a file-system database from a directory named "memory"

    Details

    • Type: Bug Bug
    • Status: Closed
    • Priority: Minor Minor
    • Resolution: Fixed
    • Affects Version/s: 10.6.1.0
    • Fix Version/s: 10.6.1.0
    • Component/s: JDBC, Services, Store
    • Labels:
      None

      Description

      With both the embedded and network client drivers, it is possible to create a file-system database and drop it, if you put it in a directory named "memory".

      I found this out by accident when I accidentally typed "memory/mydb" instead of "memory:mydb" to create an in-memory database.

      If you call the directory something other than "memory", you can't drop the db:

      ij> connect 'jdbc:derby://localhost:1527/subdir/mycdb;create=true';
      ij> create table t(c int);
      0 rows inserted/updated/deleted
      ij> connect 'jdbc:derby://localhost:1527/subdir/mycdb;drop=true';
      ERROR XBM0I: DERBY SQL error: SQLCODE: -1, SQLSTATE: XBM0I, SQLERRMC: Directory subdir/mycdb cannot be removed.

      But if you do exactly the same thing specifying "memory", the drop succeeds:

      ij> connect 'jdbc:derby://localhost:1527/memory/mycdb;create=true';
      ij> create table t(c int);
      0 rows inserted/updated/deleted
      ij> connect 'jdbc:derby://localhost:1527/memory/mycdb;drop=true';
      ERROR 08006: DERBY SQL error: SQLCODE: -1, SQLSTATE: 08006, SQLERRMC: Database 'memory/mycdb' dropped.

      When you do this, the "memory" directory continues to exist, but the database directory under it is removed.

      Here are similar examples using the embedded driver:

      ij> connect 'jdbc:derby:subdir/mydb;create=true';
      ij> create table t(c int);
      0 rows inserted/updated/deleted
      ij> connect 'jdbc:derby:subdir/mydb;drop=true';
      ERROR XBM0I: Directory subdir/mydb cannot be removed.

      ij> connect 'jdbc:derby:memory/mydb;create=true';
      ij> create table t(c int);
      0 rows inserted/updated/deleted
      ij> connect 'jdbc:derby:memory/mydb;drop=true';
      ERROR 08006: Database 'memory/mydb' dropped.

      Some part of Derby seems to think you actually created an in-memory database, although you did not.

        Issue Links

          Activity

          Hide
          Kristian Waagan added a comment -

          In some cases Derby uses protocol prefixes to determine the protocol. At the same time, the default protocol (which is formally 'directory:') is represented with no protocol prefix. In this case Derby is probably just checking if the string starts with "memory".
          I'll have a look.

          Show
          Kristian Waagan added a comment - In some cases Derby uses protocol prefixes to determine the protocol. At the same time, the default protocol (which is formally 'directory:') is represented with no protocol prefix. In this case Derby is probably just checking if the string starts with "memory". I'll have a look.
          Hide
          Kristian Waagan added a comment -

          Attaching a very simple fix for this bug. There isn't a general problem allowing one to delete on-disk databases - the database name has to start with "memory" to be able to trigger the bug.
          I'm not sure if this catches all corner-cases, but it will hopefully do. We are already using the remove service root functionality for on-disk databases internally, so we cannot disable it.

          I'll run the regression tests to be sure, but hopefully this change shouldn't cause any trouble.
          I plan to commit it tomorrow.

          Show
          Kristian Waagan added a comment - Attaching a very simple fix for this bug. There isn't a general problem allowing one to delete on-disk databases - the database name has to start with "memory" to be able to trigger the bug. I'm not sure if this catches all corner-cases, but it will hopefully do. We are already using the remove service root functionality for on-disk databases internally, so we cannot disable it. I'll run the regression tests to be sure, but hopefully this change shouldn't cause any trouble. I plan to commit it tomorrow.
          Hide
          Kristian Waagan added a comment -

          Committed 1a to trunk with revision 926600.

          Show
          Kristian Waagan added a comment - Committed 1a to trunk with revision 926600.

            People

            • Assignee:
              Kristian Waagan
              Reporter:
              Kim Haase
            • Votes:
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              Dates

              • Created:
                Updated:
                Resolved:

                Development