docs/topics/impala_disable_codegen.xml

<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="disable_codegen">

  <title>DISABLE_CODEGEN Query Option</title>

  <titlealts audience="PDF">

    <navtitle>DISABLE_CODEGEN</navtitle>

  </titlealts>

  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="Impala Query Options"/>
      <data name="Category" value="Troubleshooting"/>
      <data name="Category" value="Performance"/>
    </metadata>
  </prolog>

  <conbody>

    <p>
      The <codeph>DISABLE_CODEGEN</codeph> is a debug option, and it's used to work around any
      issues with Impala's runtime code generation. If a query fails with an <q>illegal
      instruction</q> or other hardware-specific message, try setting
      <codeph>DISABLE_CODEGEN=true</codeph> and running the query again. If the query succeeds
      only when the <codeph>DISABLE_CODEGEN</codeph> option is turned on, submit the problem to
      <keyword keyref="support_org"> </keyword> and include that detail in the problem report.
    </p>

    <p>
      Most queries will run significantly slower with <codeph>DISABLE_CODEGEN=true</codeph>.
    </p>

    <p>
      In Impala 2.10 and higher, the <codeph>DISABLE_CODEGEN_ROWS_THRESHOLD</codeph>
      optimisation automatically disables codegen for small queries because short-running
      queries may run faster without the overhead of codegen.
    </p>

    <p>
      The following values are supported:
      <ul>
        <li>
          <codeph>TRUE</codeph> or <codeph>1</codeph>: Disables codegen.
        </li>

        <li>
          <codeph>FALSE</codeph> or <codeph>0</codeph>: Enables codegen.
        </li>
      </ul>
    </p>

    <p>
      <b>Type:</b> Boolean
    </p>

    <p conref="../shared/impala_common.xml#common/default_false_0"/>

  </conbody>

</concept>