docs/topics/impala_runtime_filter_mode.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="runtime_filter_mode" rev="2.5.0">

  <title>RUNTIME_FILTER_MODE Query Option (<keyword keyref="impala25"/> or higher only)</title>
  <titlealts audience="PDF"><navtitle>RUNTIME_FILTER_MODE</navtitle></titlealts>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="Impala Query Options"/>
      <data name="Category" value="Performance"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Data Analysts"/>
    </metadata>
  </prolog>

  <conbody>

    <p rev="2.5.0">
      <indexterm audience="hidden">RUNTIME_FILTER_MODE query option</indexterm>
    </p>

    <p>
      The <codeph>RUNTIME_FILTER_MODE</codeph> query option
      adjusts the settings for the runtime filtering feature.
      It turns this feature on and off, and controls how
      extensively the filters are transmitted between hosts.
    </p>

    <p>
      <b>Type:</b> numeric (0, 1, 2)
      or corresponding mnemonic strings (<codeph>OFF</codeph>, <codeph>LOCAL</codeph>, <codeph>GLOBAL</codeph>).
    </p>

    <p rev="2.6.0">
      <b>Default:</b> 2 (equivalent to <codeph>GLOBAL</codeph>); formerly was 1 / <codeph>LOCAL</codeph>, in <keyword keyref="impala25_full"/>
    </p>

    <p conref="../shared/impala_common.xml#common/added_in_250"/>

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

    <p rev="2.6.0">
      In <keyword keyref="impala26_full"/> and higher, the default is <codeph>GLOBAL</codeph>.
      This setting is recommended for a wide variety of workloads, to provide best
      performance with <q>out of the box</q> settings.
    </p>

    <p rev="2.6.0">
      The lowest setting of <codeph>LOCAL</codeph> does a similar level of optimization
      (such as partition pruning) as in earlier Impala releases.
      This setting was the default in <keyword keyref="impala25_full"/>,
      to allow for a period of post-upgrade testing for existing workloads.
      This setting is suitable for workloads with non-performance-critical queries,
      or if the coordinator node is under heavy CPU or memory pressure.
    </p>

    <p>
      You might change the setting to <codeph>OFF</codeph> if your workload contains
      many queries involving partitioned tables or joins that do not experience a performance
      increase from the runtime filters feature. If the overhead of producing the runtime filters
      outweighs the performance benefit for queries, you can turn the feature off entirely.
    </p>

    <p conref="../shared/impala_common.xml#common/related_info"/>
    <p>
      <xref href="impala_partitioning.xml#partitioning"/> for details about runtime filtering.
      <xref href="impala_disable_row_runtime_filtering.xml#disable_row_runtime_filtering"/>,
      <xref href="impala_runtime_bloom_filter_size.xml#runtime_bloom_filter_size"/>,
      <xref href="impala_runtime_filter_wait_time_ms.xml#runtime_filter_wait_time_ms"/>,
      and
      <xref href="impala_max_num_runtime_filters.xml#max_num_runtime_filters"/>
      for tuning options for runtime filtering.
    </p>

  </conbody>
</concept>