docs/topics/impala_buffer_pool_limit.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
-->
<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="buffer_pool_limit" rev="2.10.0 IMPALA-3200">

  <title>BUFFER_POOL_LIMIT Query Option</title>
  <titlealts audience="PDF"><navtitle>BUFFER_POOL_LIMIT</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>
      <indexterm audience="hidden">BUFFER_POOL_LIMIT query option</indexterm>
      Defines a limit on the amount of memory that a query can allocate from the
      internal buffer pool. The value for this limit applies to the memory on each host,
      not the aggregate memory across the cluster. Typically not changed by users, except
      during diagnosis of out-of-memory errors during queries.
    </p>

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

<!--  BUFFER_POOL_LIMIT: [0] -->

    <p conref="../shared/impala_common.xml#common/default_blurb"/>
    <p>
      The default setting for this option is the lower of 80% of the
      <codeph>MEM_LIMIT</codeph> setting, or the <codeph>MEM_LIMIT</codeph>
      setting minus 100 MB.
    </p>

    <p conref="../shared/impala_common.xml#common/added_in_2100"/>

    <p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
    <p>
      If queries encounter out-of-memory errors, consider decreasing the
      <codeph>BUFFER_POOL_LIMIT</codeph> setting to less than 80% of the
      <codeph>MEM_LIMIT setting</codeph>.
    </p>

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

<codeblock><![CDATA[
-- Set an absolute value.
set buffer_pool_limit=8GB;

-- Set a relative value based on the MEM_LIMIT setting.
set buffer_pool_limit=80%;
]]>
</codeblock>

    <p conref="../shared/impala_common.xml#common/related_info"/>
    <p>
      <xref keyref="default_spillable_buffer_size"/>,
      <xref keyref="max_row_size"/>,
      <xref keyref="min_spillable_buffer_size"/>,
      <xref keyref="scalability_buffer_pool"/>
    </p>

  </conbody>
</concept>