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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>
90 lines
2.9 KiB
XML
90 lines
2.9 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="disable_hbase_num_rows_estimate">
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<title>DISABLE_HBASE_NUM_ROWS_ESTIMATE Query Option</title>
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<titlealts audience="PDF">
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<navtitle>DISABLE HBASE NUM ROWS ESTIMATE</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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<data name="Category" value="Performance"/>
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</metadata>
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</prolog>
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<conbody>
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<p>
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Use the <codeph>DISABLE_HBASE_NUM_ROWS_ESTIMATE</codeph> query option to disable key
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sampling of HBase tables in row count and row size estimation.
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</p>
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<p>
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While generating a plan for an HBase query, the planner samples the underlying HBase
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tables to estimate their row count and row size, and the sampling can negatively impact
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the planning time. When the HBase table stats does not change much in short time, disable
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the sampling by setting the <codeph>DISABLE_HBASE_NUM_ROWS_ESTIMATE</codeph> query option
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to <codeph>TRUE</codeph>. And Impala planner will fall back to using Hive Metastore (HMS)
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table stats instead.
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</p>
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<p>
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When <codeph>DISABLE_HBASE_NUM_ROWS_ESTIMATE</codeph> query option is set to
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<codeph>TRUE</codeph>, you need to update the HMS table stats by running <codeph>COMPUTE
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STATS</codeph>. Alternatively, you can manually set table statistics by running
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<codeph>ALTER TABLE</codeph>. See <xref
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href="impala_perf_stats.xml#perf_stats"/>
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for details.
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</p>
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<p>
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The following values are supported:
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<ul>
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<li>
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<codeph>TRUE</codeph> or <codeph>1</codeph>: Disables the normal key sampling of HBase
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tables and uses HMS table stats for estimation.
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</li>
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<li>
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<codeph>FALSE</codeph> or <codeph>0</codeph>: Enables the normal sampling of HBase
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tables.
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</li>
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</ul>
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</p>
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<p>
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<b>Type:</b> <codeph>BOOLEAN</codeph>
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</p>
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<p>
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<b>Default:</b> <codeph>FALSE</codeph>
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</p>
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</conbody>
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</concept>
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