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     <h4 class="title">
      <a name="mysql-cluster-limitations-performance">
      </a>
      25.2.7.7 Limitations Relating to Performance in NDB Cluster
     </h4>
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  <p>
   The following performance issues are specific to or especially
        pronounced in NDB Cluster:
  </p>
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     <p>
      <b>
       Range scans.
      </b>
      There are query performance issues due to sequential
              access to the
      <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
       <code class="literal">
        NDB
       </code>
      </a>
      storage
              engine; it is also relatively more expensive to do many
              range scans than it is with either
      <code class="literal">
       MyISAM
      </code>
      or
      <code class="literal">
       InnoDB
      </code>
      .
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     <p>
      <b>
       Reliability of Records in range.
      </b>
      The
      <code class="literal">
       Records in range
      </code>
      statistic is
              available but is not completely tested or officially
              supported. This may result in nonoptimal query plans in
              some cases. If necessary, you can employ
      <code class="literal">
       USE
              INDEX
      </code>
      or
      <code class="literal">
       FORCE INDEX
      </code>
      to alter
              the execution plan. See
      <a class="xref" href="index-hints.html" title="10.9.4 Index Hints">
       Section 10.9.4, “Index Hints”
      </a>
      , for
              more information on how to do this.
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     <p>
      <b>
       Unique hash indexes.
      </b>
      Unique hash indexes created with
      <code class="literal">
       USING
              HASH
      </code>
      cannot be used for accessing a table if
      <code class="literal">
       NULL
      </code>
      is given as part of the key.
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