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| <h1 class="title topictitle1" id="ariaid-title1">SHUFFLE_DISTINCT_EXPRS Query Option</h1> |
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| <p class="p"> |
| The <code class="ph codeph">SHUFFLE_DISTINCT_EXPRS</code> query option controls the |
| shuffling behavior when a query has both grouping and distinct expressions. |
| Impala can optionally include the distinct expressions in the hash exchange |
| to spread the data among more nodes. However, this plan requires one more |
| hash exchange phase. |
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| It is recommended that you turn off this option if the NDVs of the grouping |
| expressions are high. |
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| <strong class="ph b">Type:</strong> Boolean; recognized values are 1 and 0, or <code class="ph codeph">true</code> and |
| <code class="ph codeph">false</code>; any other value interpreted as <code class="ph codeph">false</code> |
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| <strong class="ph b">Default:</strong> <code class="ph codeph">false</code> |
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| <div class="parentlink"><strong>Parent topic:</strong> <a class="link" href="../topics/impala_query_options.html">Query Options for the SET Statement</a></div> |
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