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<chapter>
  <header>
    <copyright>
      <year>1996</year><year>2020</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

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      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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    <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 4.19.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
	    <p>Suppression of deprecation warnings has been added to
	    the source files of the Mnesia application.</p>
          <p>
	    Own Id: OTP-17217</p>
        </item>
        <item>
          <p>
	    Fixed that the backend plugin initialization is done only
	    once.</p>
          <p>
	    Own Id: OTP-17294 Aux Id: GH-4525 PR-4674 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.19</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed the type spec for <c>disc_only_copies</c>.</p>
          <p>
	    Own Id: OTP-17249 Aux Id: PR-4578 </p>
        </item>
        <item>
          <p>
	    Do not crash in <c>mnesia:change_config/2</c> if mnesia
	    is stopping or starting.</p>
          <p>
	    Own Id: OTP-17274 Aux Id: GH-4616 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Optimized table loading time for tables that are updated
	    during the loading.</p>
          <p>
	    Own Id: OTP-17271 Aux Id: PR-4575 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.18.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Avoid potential performance issue, if the input queue to
	    <c>mnesia_tm</c> is long.</p>
          <p>
	    Own Id: OTP-17066 Aux Id: PR-2889 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.18</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    FIx mnesia delete object handling in transaction storage.
	    In a transaction <c>mnesia:read/1</c> could indicate that
	    exiting objects did not exist after another object was
	    deleted.</p>
          <p>
	    Own Id: OTP-16782 Aux Id: PR-2663 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Fixed crash during startup, which could happen if a table
	    was deleted on another node.</p>
          <p>
	    Own Id: OTP-16815 Aux Id: ERIERL-500 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.17</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Make <c>mnesia:create_table/2</c> return correct badarg
	    value.</p>
          <p>
	    Own Id: OTP-16072 Aux Id: PR-2320 </p>
        </item>
        <item>
          <p>
	    Fixed a bug where mnesia was sometimes not waiting during
	    start for a commit decision on asymmetric transactions.</p>
          <p>
	    Own Id: OTP-16634 Aux Id: PR-2610 ERL-1227 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Remove usage and documentation of old requests of the
	    I/O-protocol.</p>
          <p>
	    Own Id: OTP-15695</p>
        </item>
        <item>
          <p>
	    Avoid using <c>rpc</c> calls to do table reads, which
	    will reduce the load on rpc server and improve
	    performance.</p>
          <p>
	    Own Id: OTP-16189</p>
        </item>
      </list>
    </section>

</section>

  <section><title>Mnesia 4.16.3.1</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Fixed crash during startup, which could happen if a table
	    was deleted on another node.</p>
          <p>
	    Own Id: OTP-16815 Aux Id: ERIERL-500 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.16.3</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed a timing issue in uninstall fallback functionality.</p>
          <p>
	    Own Id: OTP-16468 Aux Id: ERL-1151 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.16.2</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed mnesia crash which could happen when trying to
	    recover from failures in transactions containing
	    <c>sticky_locks</c>.</p>
          <p>
	    Own Id: OTP-16286 Aux Id: ERL-1077 </p>
        </item>
        <item>
          <p>
	    Fixed mnesia index issue. Could happen when updating
	    records with a index plugin backend.</p>
          <p>
	    Own Id: OTP-16291 Aux Id: ERL-1091 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.16.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    <c>mnesia:add_table_copy/3</c> could cause a deadlock if
	    called when a new node was starting.</p>
          <p>
	    Own Id: OTP-15933 Aux Id: ERL-872 </p>
        </item>
        <item>
	    <p>Transactions with sticky locks could with async_asym
	    transactions be committed in the wrong order, since asym
	    transaction are spawned on the remote nodes.</p> <p>To
	    fix this bug the communication protocol between mnesia
	    nodes had to be updated, thus mnesia will no longer be
	    able to connect to nodes earlier than mnesia-4.14 ,
	    OTP-19.0.</p>
          <p>
	    *** POTENTIAL INCOMPATIBILITY ***</p>
          <p>
	    Own Id: OTP-15979 Aux Id: ERL-768 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.16</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Optimize mnesia:read/1 if data have been written in the
	    same transaction.</p>
          <p>
	    Own Id: OTP-15550 Aux Id: PR-2029 </p>
        </item>
        <item>
          <p>
	    Fixed bugs in table index plugin handling.</p>
          <p>
	    Own Id: OTP-15689 Aux Id: PR-1695 ERL-556 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Optimized dumping of tables with plugin backends.</p>
          <p>
	    Own Id: OTP-15588 Aux Id: PR-2102 </p>
        </item>
        <item>
          <p>
	    Include stacktrace in exception if a dirty activity
	    errors, thus if user have matched on the error thrown it
	    may not match any more.</p>
          <p>
	    *** POTENTIAL INCOMPATIBILITY ***</p>
          <p>
	    Own Id: OTP-15804 Aux Id: PR-2216 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15.6</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Avoid overload warnings caused by a race condition.</p>
          <p>
	    Own Id: OTP-15619 Aux Id: ERIERL-310 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15.5</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed type spec for <c>mnesia:change_config/2</c>.</p>
          <p>
	    Own Id: OTP-15201 Aux Id: PR-1881 </p>
        </item>
        <item>
          <p>
	    When master node is set do not force a load from
	    ram_copies replica when there are no available
	    disc_copies, since that would load an empty table. Wait
	    until a disk replica is available or until user
	    explicitly force_loads the table.</p>
          <p>
	    Own Id: OTP-15221 Aux Id: ERIERL-217 </p>
        </item>
        <item>
          <p>
	    Allow to add replicas even if all other replicas are down
	    when the other replicas are not stored on disk.</p>
          <p>
	    Own Id: OTP-15226 Aux Id: ERIERL-221 </p>
        </item>
        <item>
          <p>
	    Fixed <c>mnesia:delete_object/1</c> bug, where
	    delete_object was deleting the record if it was written
	    in the same transaction even if it was written to a
	    different value.</p>
          <p>
	    Own Id: OTP-15231 Aux Id: PR-1858 </p>
        </item>
        <item>
          <p>
	    Fixed a bug where the bag table index data was not
	    deleted when objects were deleted.</p>
          <p>
	    Own Id: OTP-15243</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15.4</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
	    <p> Calls to <c>erlang:get_stacktrace()</c> are removed.
	    </p>
          <p>
	    Own Id: OTP-14861</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15.3.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    When master node is set do not force a load from
	    ram_copies replica when there are no available
	    disc_copies, since that would load an empty table. Wait
	    until a disk replica is available or until user
	    explicitly force_loads the table.</p>
          <p>
	    Own Id: OTP-15221 Aux Id: ERIERL-217 </p>
        </item>
        <item>
          <p>
	    Allow to add replicas even if all other replicas are down
	    when the other replicase are not stored on disk.</p>
          <p>
	    Own Id: OTP-15226 Aux Id: ERIERL-221 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15.3</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Removed a quadratic behavior in startup. This change
	    implies that backend plugins (if used) must be set when
	    the schema is created or via configuration parameters
	    before mnesia is started.</p>
          <p>
	    Own Id: OTP-14829 Aux Id: ERIERL-84 </p>
        </item>
        <item>
          <p>
	    Bad timing could crash mnesia after a checkpoint was
	    deactivated and reactivated with the same checkpoint name
	    on different tables.</p>
          <p>
	    Own Id: OTP-14841 Aux Id: ERIERL-113 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15.2</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fix backup error handling, the real failure reason was
	    not returned.</p>
          <p>
	    Own Id: OTP-14776 Aux Id: ERIERL-103 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15.1</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    General Unicode improvements.</p>
          <p>
	    Own Id: OTP-14462</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.15</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Removed the wrapping of select continuations in extension
	    plugin handling. This might require the user to rewrite
	    user backend plugin if used.</p>
          <p>
	    *** POTENTIAL INCOMPATIBILITY ***</p>
          <p>
	    Own Id: OTP-14039</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.14.3</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed crash in checkpoint handling when table was deleted
	    during backup.</p>
          <p>
	    Own Id: OTP-14167</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.14.2</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    A continuation returned by mnesia:select/[14] should be
	    reusable in different, non-transactional activities.</p>
          <p>
	    Own Id: OTP-13944 Aux Id: PR-1184 </p>
        </item>
        <item>
          <p>
	    Fixed crash when calling block_table multiple times.
	    Could happen when having locks for a long time and
	    restarting mnesia.</p>
          <p>
	    Own Id: OTP-13970 Aux Id: Seq-13198 </p>
        </item>
        <item>
          <p>
	    Change mnesia_tm process to have off-heap messages since
	    mnesia_tm can be the receiver of many non-synchronized
	    message from other nodes.</p>
          <p>
	    Own Id: OTP-14074</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.14.1</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
	    <p> Correct some minor documentation issues. </p>
          <p>
	    Own Id: OTP-13891</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.14</title>

    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Added experimental external backend plugin api. This adds
	    the possibility for the user to write other storage
	    backends for data, for example by using shared memory or
	    ram-cached disk storage.</p>
          <p>
	    The plugin api may change in future versions after being
	    battle tested.</p>
          <p>
	    Own Id: OTP-13058</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.13.4</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Mnesia transactions could hang while waiting on a
	    response from a node who had stopped.</p>
          <p>
	    Own Id: OTP-13423</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.13.3</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Avoid deadlock possibility in
	    <c>mnesia:del_table_copy/2</c></p>
          <p>
	    Own Id: OTP-13284</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.13.2</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed a process and file descriptor leak in
	    mnesia:restore/2.</p>
          <p>
	    Own Id: OTP-13025 Aux Id: seq12957 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.13.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Improved index updates to avoid a timing glitch in
	    dirty_index_read.</p>
          <p>
	    Own Id: OTP-12972</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.13</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Mnesia's dirty functions did not always exit with
	    <c>{aborted, Reason}</c> as documented when an error
	    occurred.</p>
          <p>
	    Own Id: OTP-12714</p>
        </item>
        <item>
          <p>
	    Consider file descriptors limits (emfile) as a fatal
	    error and do not delete log files. Previously the error
	    was seen as a corrupted disk and the log files deleted
	    which caused data loss.</p>
          <p>
	    Own Id: OTP-12807</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Make Mnesia DCD dump behavior at start up optional, when
	    turned off mnesia loads large disc_copies tables faster.</p>
          <p>
	    Own Id: OTP-12481</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.12.5</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed race condition in protocol negotiation.</p>
          <p>
	    Own Id: OTP-12473</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Grammar corrections. (Thanks to Derek Brown)</p>
          <p>
	    Own Id: OTP-12400</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.12.4</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed a spelling mistake in mnesia documentation.</p>
          <p>
	    Own Id: OTP-12278</p>
        </item>
        <item>
          <p>
	    Matching data with <c>mnesia:match_object/1</c> did not
	    work as expected in some cases, when data was written in
	    the same transaction before the matching was invoked.</p>
          <p>
	    Own Id: OTP-12304 Aux Id: Seq12745 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.12.3</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Various logging fixes, including: Add run queue index to
	    the process dump in crash dumps.<br/> Add thread index to
	    enomem slogan when crashing.<br/> Remove error logger
	    message for sending messages to old instances of the same
	    node.</p>
          <p>
	    Own Id: OTP-12115</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.12.2</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed a race which could make create_table fail if a node
	    was going down during the transaction.</p>
          <p>
	    Own Id: OTP-12124 Aux Id: seq12694 </p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.12.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Force load table could hang when a node went away during
	    start up.</p>
          <p>
	    Own Id: OTP-11948 Aux Id: seq12585 </p>
        </item>
        <item>
          <p>
	    The time for inserting locks for a transaction with large
	    number of locks is reduced significantly.</p>
          <p>
	    Own Id: OTP-11981</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.12</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Some local implementations of removing the last element
	    from a list are replaced by <c>lists:droplast/1</c>. Note
	    that this requires at least <c>stdlib-2.0</c>, which is
	    the stdlib version delivered in OTP 17.0. (Thanks to Hans
	    Svensson)</p>
          <p>
	    Own Id: OTP-11678</p>
        </item>
        <item>
          <p>
	    Application upgrade (appup) files are corrected for the
	    following applications: </p>
          <p>
	    <c>asn1, common_test, compiler, crypto, debugger,
	    dialyzer, edoc, eldap, erl_docgen, et, eunit, gs, hipe,
	    inets, observer, odbc, os_mon, otp_mibs, parsetools,
	    percept, public_key, reltool, runtime_tools, ssh,
	    syntax_tools, test_server, tools, typer, webtool, wx,
	    xmerl</c></p>
          <p>
	    A new test utility for testing appup files is added to
	    test_server. This is now used by most applications in
	    OTP.</p>
          <p>
	    (Thanks to Tobias Schlager)</p>
          <p>
	    Own Id: OTP-11744</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    To prevent a race condition if there is a short
	    communication problem when node-down and node-up events
	    are received. They are now stored and later checked if
	    the node came up just before mnesia flagged the node as
	    down. (Thanks to Jonas Falkevik )</p>
          <p>
	    Own Id: OTP-11497</p>
        </item>
        <item>
          <p>
	    Added <c>mnesia:sync_log/0</c> to explicit sync mnesias
	    transaction log.</p>
          <p>
	    Own Id: OTP-11729</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.11</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fixed a race in mnesia which could cause hanging
	    transaction when sticky locks had been used. Thanks
	    janchochol.</p>
          <p>
	    Own Id: OTP-11375</p>
        </item>
        <item>
          <p>
	    Fixed dirty_update_counter which could return ok, thanks
	    Anton Ryabkov.</p>
          <p>
	    Own Id: OTP-11485</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.10</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Fix timing issues in checkpoint creation.</p>
          <p>
	    Own Id: OTP-10957</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Fixed a problem where the fallback BUP file is removed
	    when calling mnesia:uninstall_fallback and mnesia is not
	    started.</p>
          <p>
	    Own Id: OTP-11241</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.9</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    If mnesia:clear_table/2 was called during a table load on
	    that table, the schema record was written to the table
	    instead of clearing table.</p>
          <p>
	    Own Id: OTP-11030 Aux Id: seq12267 </p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Optimize index creation for Mnesia set tables. Thanks to
	    Nick Marino.</p>
          <p>
	    Own Id: OTP-11103</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.8</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Use chained send_after instead of send_interval, to make
	    decrease the number of messages sent after a sleep
	    (Thanks to James Wheare)</p>
          <p>
	    Own Id: OTP-10636</p>
        </item>
        <item>
          <p>
	    Fix format of mnesia overload message (Thanks to Ahmed
	    Omar)</p>
          <p>
	    Own Id: OTP-10639</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Added a general framework for executing benchmarks of
	    Erlang/OTP. Benchmarks for the Erlang VM and mnesia have
	    been incorporated in the framework. </p>
          <p>
	    For details about how to add more benchmarks see
	    $ERL_TOP/HOWTO/BENCHMARKS.md in the source distribution.</p>
          <p>
	    Own Id: OTP-10156</p>
        </item>
        <item>
	    <p>Where necessary a comment stating encoding has been
	    added to Erlang files. The comment is meant to be removed
	    in Erlang/OTP R17B when UTF-8 becomes the default
	    encoding. </p>
          <p>
	    Own Id: OTP-10630</p>
        </item>
        <item>
          <p>
	    Remove support for the query keyword and query
	    expressions. Thanks to Loïc Hoguin.</p>
          <p>
	    Own Id: OTP-10729</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.7.1</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Add tests showing that trying to delete non-existing
	    object may corrupt the </p>
          <p>
	    In case of bag tables, trying to delete a non-existing
	    object leads to the index becoming corrupt. This happens
	    if the non-existing object we try to delete happens to
	    share its key and index field value with a single
	    existing object in the table. Result: The index entry
	    corresponding to the existing object is removed.</p>
          <p>
	    Prevent index from being corrupted if a nonexistent item
	    is deleted</p>
          <p>
	    We have to ensure that we actually delete the last object
	    with a given (key, index) pair before removing the index.
	    Thanks to Bartlomiej Puzon</p>
          <p>
	    Own Id: OTP-10220</p>
        </item>
      </list>
    </section>

</section>

<section><title>Mnesia 4.7</title>

    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
	    Returns the same value for
	    mnesia_loader:disc_load_table/2 as
	    mnesia_loader:net_load_table/4 if a table copy cannot be
	    found. (Thanks to Uwe Dauernheim)</p>
          <p>
	    Own Id: OTP-10015</p>
        </item>
      </list>
    </section>


    <section><title>Improvements and New Features</title>
      <list>
        <item>
          <p>
	    Improved table lock algorithm.</p>
          <p>
	    Own Id: OTP-9890</p>
        </item>
      </list>
    </section>

</section>

<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 Weiß)</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>

</chapter>
