docs/topics/impala_spool_query_results.xml

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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="SPOOL_QUERY_RESULTS" rev="2.10.0 IMPALA-3200">
  <title>SPOOL_QUERY_RESULTS Query Option</title>
  <titlealts audience="PDF">
    <navtitle>SPOOL QUERY RESULTS</navtitle>
  </titlealts>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="Impala Query Options"/>
      <data name="Category" value="Querying"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Data Analysts"/>
    </metadata>
  </prolog>
  <conbody>
    <p>Use the <codeph>SPOOL_QUERY_RESULTS</codeph> query option to enable query
      result spooling, which is disabled by default.</p>
    <p>Query result spooling controls how rows are returned to the client. <ul>
        <li>When query result spooling is disabled (<codeph>SPOOL_QUERY_RESULTS
            = FALSE</codeph>), Impala relies on clients to fetch results to
          trigger the generation of more result row batches until all the result
          rows have been produced. If a client issues a query without fetching
          all the results, the query fragments will continue to consume the
          resources until the query is cancelled and unregistered, potentially
          tying up resources and cause other queries to wait for extended period
          of time in admission control.</li>
        <li>When query result spooling is enabled (<codeph>SPOOL_QUERY_RESULTS =
            TRUE</codeph>), the result sets of queries are eagerly fetched and
          spooled, either in memory or on disk. <p>Once all result rows have
            been fetched and stored in the spooling location, the resources are
            freed up. Incoming client fetches can get the data from the spooled
            results.</p></li>
      </ul></p>
    <p><b>Type:</b>
      <codeph>BOOLEAN</codeph></p>
    <p><b>Default:</b>
      <codeph>FALSE</codeph></p>
    <p><b>Added in:</b>
      <keyword keyref="impala34"/></p>
    <p><b>Related information:</b>
      <xref
        href="impala_default_spillable_buffer_size.xml#default_spillable_buffer_size"
      />, <xref
        href="impala_max_spilled_result_spooling_mem.xml#MAX_SPILLED_RESULT_SPOOLING_MEM"
      />, <xref
        href="impala_max_result_spooling_mem.xml#MAX_RESULT_SPOOLING_MEM"/></p>
  </conbody>
</concept>