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| <h1 class="title topictitle1" id="ariaid-title1">ENABLE_EXPR_REWRITES Query Option</h1> |
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| <p class="p"> |
| The <code class="ph codeph">ENABLE_EXPR_REWRITES</code> query option controls whether to enable or |
| disable the query compile time optimizations. These optimizations rewrite the expression |
| trees to a more compact and optimized form that helps avoid redundant expression |
| evaluation at run time. Performance optimizations controlled by this query option include: |
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| <ul class="ul"> |
| <li class="li"> |
| Constant folding (added in <span class="keyword">)</span> |
| </li> |
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| <li class="li"> |
| Extracting common conjuncts from disjunctions (added in |
| <span class="keyword">)</span> |
| </li> |
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| <li class="li"> |
| Simplify conditionals with constant conditions (added in |
| <span class="keyword">)</span> |
| </li> |
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| </ul> |
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| <p class="p"> |
| Set the option to <code class="ph codeph">false</code> or <code class="ph codeph">0</code> to disable the performance |
| optimizations. |
| </p> |
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| <p class="p"> |
| <strong class="ph b">Type: </strong><code class="ph codeph">boolean</code> |
| </p> |
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| <p class="p"> |
| <strong class="ph b">Default:</strong> <code class="ph codeph">true</code> (<code class="ph codeph">1</code>) |
| </p> |
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| <p class="p"> |
| <strong class="ph b">Added in:</strong> <span class="keyword">Impala 2.8</span> |
| </p> |
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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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