path: root/lib/mnesia/doc/src/notes.xml

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<!DOCTYPE chapter SYSTEM "chapter.dtd">

<chapter>
  <header>
    <copyright>
      <year>1996</year><year>2011</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 4.6</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Reduce calls to phash in key_to_frag_number</p>
          <p>
	    Original code calls phash 1..2 times, based on which
	    fragment the hashed key targets and how many fragments
	    exist. New code always calls phash only once.</p>
          <p>
	    Add mnesia_frag_hash test (Thanks to Philip Robinson)</p>
          <p>
	    Own Id: OTP-9722</p>
        </item>
        <item>
          <p>
	    Fixed a sticky lock bug which caused mnesia:read(Tab,
	    Key, write) return undefined.</p>
          <p>
	    Own Id: OTP-9786</p>
        </item>
        <item>
          <p>
	    Use the synchronous log_terms instead of alog_terms in
	    mnesia_log:ets2dcd()</p>
          <p>
	    This avoids the situation where mnesia could dump a very
	    large ets table in its entirety into the message queue of
	    the disk_log process, causing memory blowup and choking
	    the disk logger. (Thanks to Richard Carlsson)</p>
          <p>
	    Own Id: OTP-9804</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Implemented a new option to mnesia:create_table/2 which
	    allows the user to assign 'ets' and 'dets' options not
	    available in mnesia.</p>
          <p>
	    Own Id: OTP-8970</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.5.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fix deadlock in mnesia:del_table_copy/2.</p>
          <p>
	    Own Id: OTP-9689 Aux Id: seq11927 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Allow schema operations when using different mnesia
	    versions.</p>
          <p>
	    Own Id: OTP-9657 Aux Id: seq11926 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.5</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fix protocol issues. Mnesia-4.4.19 could not communicate
	    with to older nodes.</p>
          <p>
	    Own Id: OTP-9473</p>
        </item>
        <item>
	    <p> XML files have been corrected. </p>
          <p>
	    Own Id: OTP-9550 Aux Id: OTP-9541 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Dump the log even if no transactions have been invoked on
	    local node, otherwise the log will grow forever with
	    decisions from the other nodes who have tables on disk.
	    Thanks Marek Majkowski.</p>
          <p>
	    Own Id: OTP-9551</p>
        </item>
        <item>
          <p>
	    Use dedicated api for clear_table, i.e. instead of
	    match_delete use delete_all_objects. Thanks KukHyun Lee.</p>
          <p>
	    Own Id: OTP-9558</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.4.19</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Mnesia could crash if mnesia:add_table_index/2 was
	    invoked before the table was loaded on all nodes.</p>
          <p>
	    Own Id: OTP-9285 Aux Id: seq11844 </p>
        </item>
        <item>
          <p>
	    Add {majority, boolean()} per-table option.</p>
          <p>
	    With {majority, true} set for a table, write transactions
	    will abort if they cannot commit to a majority of the
	    nodes that have a copy of the table. Currently, the
	    implementation hooks into the prepare_commit, and forces
	    an asymmetric transaction if the commit set affects any
	    table with the majority flag set. In the commit itself,
	    the transaction will abort if it cannot satisfy the
	    majority requirement for all tables involved in the
	    transaction.(Thanks to Ulf Wiger)</p>
          <p>
	    Own Id: OTP-9304</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.4.18</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Call chmod without the "-f" flag</p>
          <p>
	    "-f" is a non-standard chmod option which at least SGI
	    IRIX and HP UX do not support. As the only effect of the
	    "-f" flag is to suppress warning messages, it can be
	    safely omitted. (Thanks to Holger Wei�)</p>
          <p>
	    Own Id: OTP-9170</p>
        </item>
        <item>
          <p>
	    Mnesia sometimes failed to update meta-information in
	    large systems, which could cause table content to be
	    inconsistent between nodes.</p>
          <p>
	    Own Id: OTP-9186 Aux Id: seq11728 </p>
        </item>
      </list>
    </section>

</section>

<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>