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<chapter>
  <header>
    <copyright>
      <year>1996</year><year>2010</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.

      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.

    </legalnotice>

    <title>Mnesia Release Notes</title>
    <prepared>Dan Gudmundsson and H&aring;kan Mattsson</prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date>05-01-26</date>
    <rev>AE</rev>
    <file>notes.xml</file>
  </header>
  <p>This document describes the changes made to the Mnesia system
    from version to version.  The intention of this document is to
    list all incompatibilities as well as all enhancements and
    bugfixes for every release of Mnesia. Each release of Mnesia
    thus constitutes one section in this document. The title of each
    section is the version number of Mnesia.</p>

  <section><title>Mnesia 4.4.17</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Calling mnesia:first/1 on empty fragmented table works.
	    Thanks Magnus Henoch.</p>
          <p>
	    Own Id: OTP-9108</p>
        </item>
        <item>
          <p>
	    If Mnesia detects that the network is not fully connected
	    during start, Mnesia will not start until all nodes are
	    reachable.</p>
          <p>
	    Own Id: OTP-9115 Aux Id: seq-11728 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Fix issues reported by dialyzer.</p>
          <p>
	    Own Id: OTP-9107</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.4.16</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Sometimes a 'log_header' record was added to tables when
	    invoking mnesia:restore/2 with the option
	    'recreate_tables'. Thanks Vance Shipley.</p>
          <p>
	    Own Id: OTP-8960</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Compiler warnings were eliminated.</p>
          <p>
	    Own Id: OTP-8855</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.4.15</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Eliminated warnings for auto-imported BIF clashes.</p>
          <p>
	    Own Id: OTP-8840</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.4.14</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            Added mnesia:subscribe(activity) contributed by Bernard
            Duggan.</p>
          <p>
            Own Id: OTP-8519</p>
        </item>
      </list>
    </section>
    
  </section>  
  
  <section><title>Mnesia 4.4.13</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Transactions could be left hanging if a node went down
            when invoking mnesia:sync_transaction/[1,2]. Thanks Igor
            Ribeiro Sucupira.</p>
          <p>
            Own Id: OTP-8402</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            Igor Ribeiro Sucupira added the option to compress data
            when copying tables between Mnesia nodes.</p>
          <p>
            Own Id: OTP-8406</p>
        </item>
      </list>
    </section>

  </section>
  <section><title>Mnesia 4.4.12</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            The documentation is now built with open source tools
            (xsltproc and fop) that exists on most platforms. One
            visible change is that the frames are removed.</p>
          <p>
            Own Id: OTP-8250</p>
        </item>
      </list>
    </section>

  </section>
  <section><title>Mnesia 4.4.11</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            Fixed duplicate results with mnesia:index_read() on
            ordered_set tables. Reported by Sam Bobroff. </p>
	  <p>
	    Fixed locking in mnesia:index_read() which now grabs a read
            table lock to ensure correctness, this may slow down the
            operation or block other processes trying to reach the
            same table. </p>
	  <p>
	    Calling mnesia:dump_log() could crash mnesia,
            Reported by Igor Ribeiro Sucupira.</p>
          <p> Own Id: OTP-8074</p>
        </item>
      </list>
    </section>

  </section>
  <section><title>Mnesia 4.4.10</title>
    
    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Mnesia crashed if a qlc query was running inside a
            transaction when mnesia stopped at another node. Thanks
            Teemu Antti-Poika.</p>
          <p>
            Own Id: OTP-7968</p>
        </item>
        <item>
          <p>
            Mnesia could crash when loading local_content tables.</p>
          <p>
            Own Id: OTP-8002 Aux Id: seq11277 </p>
        </item>
      </list>
    </section>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            Minor (smp) optimizations.</p>
          <p>
            Own Id: OTP-7928</p>
        </item>
      </list>
    </section>
    
  </section>


  <section><title>Mnesia 4.4.9</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            mnesia:clear_table/1 crashed instead of returning
            <c>{aborted,..}</c> if it was called inside a
            transaction.</p>
          <p>
            Own Id: OTP-7911</p>
        </item>
      </list>
    </section>
    
  </section>

  <section><title>Mnesia 4.4.8</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            With bad timing several api functions could return or
            exit with a bad error message when mnesia was shutting
            down.</p>
          <p>
            Own Id: OTP-7753 Aux Id: seq11179 </p>
        </item>
        <item>
          <p>
            <c>mnesia:clear_table/1</c> cleared all nodes table
            content even if the table was <c>local_content</c> only
            type.</p>
          <p>
            Own Id: OTP-7835</p>
        </item>
      </list>
    </section>
    
  </section>

 <section><title>Mnesia 4.4.7</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Disallowed match patterns ('_', and '$n') as argument to
            <c>mnesia:delete_object/1</c> and friends.</p>
          <p>
            Own Id: OTP-7524</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            Introduced a few new functions in Mnesia: <c>mnesia:read/2</c>,
            <c>mnesia:first/3</c>, <c>mnesia:last/3</c>, <c>mnesia:prev/4</c>,
            <c>mnesia:next/4</c>, <c>mnesia_frag:first/1</c>, <c>mnesia_frag:last/1</c>,
            <c>mnesia_frag:prev/2</c>, <c>mnesia_frag:next/2</c>.</p>
          <p>
            Own Id: OTP-7625</p>
        </item>
      </list>
    </section>

</section>

 <section><title>Mnesia 4.4.6</title>    
    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            <c>mnesia:restore/2</c> aborted if a <c>EXIT</c> message
            appeared in the client message queue.</p>
          <p>
            Own Id: OTP-7585 Aux Id: seq11046 </p>
        </item>
      </list>
    </section>
  </section>

  <section><title>Mnesia 4.4.5</title>
    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    mnesia:clear_table/1 does not require that all
            replicas of the table are available anymore.</p>
          <p>
            Own Id: OTP-7466 Aux Id: seq11015</p>
        </item>
      </list>
    </section>
  </section>

  <section><title>Mnesia 4.4.4</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Mnesia did not garbage collect transaction decisions on
            disk based nodes if no transactions where made on the
            local node.</p>
          <p>
            Own Id: OTP-7419</p>
        </item>
      </list>
    </section>

  </section>

  <section><title>Mnesia 4.4.3</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Table referred to by foreign key did not have node_pool
            properly cleaned up when a node was removed from the
            schema. Thanks Paul Mineiro.</p>
          <p>
            Own Id: OTP-7340</p>
        </item>
        <item>
          <p>
            Mnesia crashed and generated a core dump if a
            schema_transaction was running when mnesia stopped.</p>
          <p>
            Own Id: OTP-7378 Aux Id: seq10964 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            It is now possible to delete a db node even when other
            disk resident nodes are down. Thanks Paul Mineiro.</p>
          <p>
            Own Id: OTP-7383</p>
        </item>
      </list>
    </section>

</section>

  <section><title>Mnesia 4.4.2</title>
    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Sticky locks could lead to hanging transactions.</p>
          <p>
            Own Id: OTP-7205 Aux Id: seq10793 </p>
        </item>
        <item>
          <p>
            <c>mnesia:snmp_get_next_index/2</c> didn't work with
            partial index keys. Argument checking is now done
            according to documentation, in functions
            <c>mnesia:snmp_get_row/2</c>,
            <c>mnesia:snmp_get_mnesia_key/2</c> and
            <c>mnesia:snmp_get_next_index/2</c>. These functions now
            require that <c>RowIndex</c> is a list.</p>
          <p>
            *** POTENTIAL INCOMPATIBILITY ***</p>
          <p>
            Own Id: OTP-7208</p>
        </item>
      </list>
    </section>
  </section>

  <section><title>Mnesia 4.4.1</title>
    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Snmp index tables was not initialized correctly in
            <c>mnesia-4.4</c>.</p>
          <p>
            Own Id: OTP-7170 Aux Id: seq10870 </p>
        </item>
      </list>
    </section>
    <section><title>Known Bugs and Problems</title>
      <list>
        <item>
          <p>
            Rearranging fragmented tables is an O(N^2) operation.</p>
          <p>
            Own Id: OTP-6300</p>
        </item>
      </list>
    </section>
  </section>

  <section><title>Mnesia 4.4</title>
    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Mnesia ignored the module argument to
            <c>mnesia:restore/2</c>. Thanks Paul Minerio.</p>
          <p>
            Own Id: OTP-6981</p>
        </item>
      </list>
    </section>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
            Mnesia's snmp operations <c>snmp_get_row/2</c>,
            <c>snmp_get_next_index/2</c> and
            <c>snmp_get_mnesia_key/2</c> have been made context
            aware, i.e. inside a transaction they will compensate for
            table updates made in earlier in the same transaction.
            This might cause a performance drop if a lot of updates
            have been made before the invocation of these functions.</p>
          <p>
            *** POTENTIAL INCOMPATIBILITY ***</p>
          <p>
            Own Id: OTP-6856 Aux Id: seq10671 </p>
        </item>
        <item>
          <p>
            Introduced erlang:phash/2 as new default for fragmented
            tables. Already existing tables will continue to use
            whatever hash function they where using.</p>
          <p>
            Own Id: OTP-6923</p>
        </item>
        <item>
          <p>
            Introduced <c>mnesia:is_transaction/0</c>.</p>
          <p>
            Own Id: OTP-6995 Aux Id: seq10812 </p>
        </item>
      </list>
    </section>

    <section><title>Known Bugs and Problems</title>
      <list>
        <item>
          <p>
            Rearranging fragmented tables is an O(N^2) operation.</p>
          <p>
            Own Id: OTP-6300</p>
        </item>
      </list>
    </section>
  </section>

  <!-- section>
    <title>Previous Notes</title>
    <p>For information about older versions see <url href="part_notes_history_frame.html">release notes history</url>.</p>
  </section -->
</chapter>

