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eadd35f6d5
The recent documentation formatting changes introduced the navigation panel on the left. However, due to the length of the query options navigation title these could overlap with the documentation paragraphs. This commit removes the underscores from the navigation titles of the query options, so browsers can break them into multiple lines. Additionally, the "SET" and "Query Options for the SET Statement" pages are merged to save some more space for the query option navigation titles. Testing: - Built the documentation and tested manually Change-Id: Icec787d7a2af848aaaff65be2ecf311a5ce8fe7f Reviewed-on: http://gerrit.cloudera.org:8080/20556 Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com> Reviewed-by: Jason Fehr <jfehr@cloudera.com> Reviewed-by: Peter Rozsa <prozsa@cloudera.com> Reviewed-by: Tamas Mate <tmater@apache.org>
72 lines
3.2 KiB
XML
72 lines
3.2 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 rev="2.0.0" id="disable_unsafe_spills">
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<title>DISABLE_UNSAFE_SPILLS Query Option (<keyword keyref="impala20"/> or higher only)</title>
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<titlealts audience="PDF"><navtitle>DISABLE UNSAFE SPILLS</navtitle></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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<data name="Category" value="Performance"/>
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<data name="Category" value="Scalability"/>
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<data name="Category" value="Memory"/>
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<data name="Category" value="Developers"/>
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<data name="Category" value="Data Analysts"/>
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</metadata>
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</prolog>
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<conbody>
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<p rev="2.0.0">
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<indexterm audience="hidden">DISABLE_UNSAFE_SPILLS query option</indexterm>
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Enable this option if you prefer to have queries fail when they exceed the Impala memory limit, rather than
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write temporary data to disk.
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</p>
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<p>
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Queries that <q>spill</q> to disk typically complete successfully, when in earlier Impala releases they would have failed.
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However, queries with exorbitant memory requirements due to missing statistics or inefficient join clauses could
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become so slow as a result that you would rather have them cancelled automatically and reduce the memory
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usage through standard Impala tuning techniques.
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</p>
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<p>
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This option prevents only <q>unsafe</q> spill operations, meaning that one or more tables are missing
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statistics or the query does not include a hint to set the most efficient mechanism for a join or
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<codeph>INSERT ... SELECT</codeph> into a partitioned table. These are the tables most likely to result in
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suboptimal execution plans that could cause unnecessary spilling. Therefore, leaving this option enabled is a
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good way to find tables on which to run the <codeph>COMPUTE STATS</codeph> statement.
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</p>
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<p>
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See <xref href="impala_scalability.xml#spill_to_disk"/> for information about the <q>spill to disk</q>
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feature for queries processing large result sets with joins, <codeph>ORDER BY</codeph>, <codeph>GROUP
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BY</codeph>, <codeph>DISTINCT</codeph>, aggregation functions, or analytic functions.
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</p>
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<p conref="../shared/impala_common.xml#common/type_boolean"/>
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<p conref="../shared/impala_common.xml#common/default_false_0"/>
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<p conref="../shared/impala_common.xml#common/added_in_20"/>
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</conbody>
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</concept>
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