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15f0ea9476
- Minor edit Change-Id: I2f7eaacd5a885a7a5292d7694241d58e4f7b6282 (cherry picked from commit 0f1c87f814b5af4f6b37c5ebf095e887916424ef) Reviewed-on: http://gerrit.cloudera.org:8080/15457 Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com> Reviewed-by: Aman Sinha <amsinha@cloudera.com> Reviewed-by: Joe McDonnell <joemcdonnell@cloudera.com>
68 lines
2.3 KiB
XML
68 lines
2.3 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
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<concept id="broadcast_bytes_limit">
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<title>BROADCAST_BYTES_LIMIT Query Option</title>
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<titlealts audience="PDF">
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<navtitle>BROADCAST_BYTES_LIMIT</navtitle>
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</titlealts>
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<prolog>
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<metadata>
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<data name="Category" value="Impala"/>
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<data name="Category" value="Impala Query Options"/>
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</metadata>
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</prolog>
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<conbody>
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<p>
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<indexterm audience="hidden">BROADCAST_BYTES_LIMIT query option</indexterm> Sets the limit
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for the size of the broadcast input based on estimated size.
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</p>
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<p>
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The Impala planner may in rare cases make a bad choice to broadcast a large table or intermediate
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result and encounter performance problems due to high memory pressure. Setting this limit will
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make the planner pick a partition based hash join instead of broadcast and avoid such performance problems.
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</p>
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<p conref="../shared/impala_common.xml#common/type_integer"/>
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<p conref="../shared/impala_common.xml#common/default_blurb"/>
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<p>
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The default value is 34359738368 (32 GB). A value of 0 causes the option to be ignored.
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</p>
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<p conref="../shared/impala_common.xml#common/example_blurb"/>
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<codeblock><![CDATA[
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-- Change the limit to 16GB.
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set broadcast_bytes_limit=17179869184;
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-- Disable the BROADCAST_BYTES_LIMIT.
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set broadcast_bytes_limit=0;
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]]>
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</codeblock>
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</conbody>
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</concept>
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