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8377b9949c
For this change to land in master, the audience="hidden" code review needs to be completed first. Otherwise, the doc build would still work but the audience="hidden" content would be visible rather than hidden as desired. Some work happening in parallel might introduce additional instances of audience="Cloudera". I suggest addressing those in a followup CR so this global change can land quickly. Since the changes apply across so many different files, but are so narrow in scope, I suggest that the way to validate (check that no extraneous changes were introduced accidentally) is to diff just the changed lines: git diff -U0 HEAD^ HEAD In patch set 2, I updated other topics marked audience="Cloudera" by CRs that were pushed in the meantime. Change-Id: Ic93d89da77e1f51bbf548a522d98d0c4e2fb31c8 Reviewed-on: http://gerrit.cloudera.org:8080/5613 Reviewed-by: John Russell <jrussell@cloudera.com> Tested-by: Impala Public Jenkins
156 lines
6.4 KiB
XML
156 lines
6.4 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="create_database">
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<title>CREATE DATABASE Statement</title>
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<titlealts audience="PDF"><navtitle>CREATE DATABASE</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="SQL"/>
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<data name="Category" value="Databases"/>
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<data name="Category" value="Schemas"/>
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<data name="Category" value="DDL"/>
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<data name="Category" value="S3"/>
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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>
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<indexterm audience="hidden">CREATE DATABASE statement</indexterm>
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Creates a new database.
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</p>
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<p>
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In Impala, a database is both:
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</p>
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<ul>
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<li>
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A logical construct for grouping together related tables, views, and functions within their own namespace.
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You might use a separate database for each application, set of related tables, or round of experimentation.
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</li>
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<li>
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A physical construct represented by a directory tree in HDFS. Tables (internal tables), partitions, and
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data files are all located under this directory. You can perform HDFS-level operations such as backing it up and measuring space usage,
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or remove it with a <codeph>DROP DATABASE</codeph> statement.
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</li>
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</ul>
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<p conref="../shared/impala_common.xml#common/syntax_blurb"/>
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<codeblock>CREATE (DATABASE|SCHEMA) [IF NOT EXISTS] <varname>database_name</varname>[COMMENT '<varname>database_comment</varname>']
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[LOCATION <varname>hdfs_path</varname>];</codeblock>
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<p conref="../shared/impala_common.xml#common/ddl_blurb"/>
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<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
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<p>
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A database is physically represented as a directory in HDFS, with a filename extension <codeph>.db</codeph>,
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under the main Impala data directory. If the associated HDFS directory does not exist, it is created for you.
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All databases and their associated directories are top-level objects, with no physical or logical nesting.
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</p>
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<p>
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After creating a database, to make it the current database within an <cmdname>impala-shell</cmdname> session,
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use the <codeph>USE</codeph> statement. You can refer to tables in the current database without prepending
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any qualifier to their names.
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</p>
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<p>
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When you first connect to Impala through <cmdname>impala-shell</cmdname>, the database you start in (before
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issuing any <codeph>CREATE DATABASE</codeph> or <codeph>USE</codeph> statements) is named
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<codeph>default</codeph>.
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</p>
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<p conref="../shared/impala_common.xml#common/builtins_db"/>
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<p>
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After creating a database, your <cmdname>impala-shell</cmdname> session or another
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<cmdname>impala-shell</cmdname> connected to the same node can immediately access that database. To access
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the database through the Impala daemon on a different node, issue the <codeph>INVALIDATE METADATA</codeph>
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statement first while connected to that other node.
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</p>
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<p>
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Setting the <codeph>LOCATION</codeph> attribute for a new database is a way to work with sets of files in an
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HDFS directory structure outside the default Impala data directory, as opposed to setting the
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<codeph>LOCATION</codeph> attribute for each individual table.
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</p>
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<p conref="../shared/impala_common.xml#common/sync_ddl_blurb"/>
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<p conref="../shared/impala_common.xml#common/hive_blurb"/>
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<p>
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When you create a database in Impala, the database can also be used by Hive.
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When you create a database in Hive, issue an <codeph>INVALIDATE METADATA</codeph>
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statement in Impala to make Impala permanently aware of the new database.
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</p>
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<p>
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The <codeph>SHOW DATABASES</codeph> statement lists all databases, or the databases whose name
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matches a wildcard pattern. <ph rev="2.5.0">In <keyword keyref="impala25_full"/> and higher, the
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<codeph>SHOW DATABASES</codeph> output includes a second column that displays the associated
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comment, if any, for each database.</ph>
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</p>
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<p conref="../shared/impala_common.xml#common/s3_blurb"/>
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<p rev="2.6.0 CDH-39913 IMPALA-1878">
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To specify that any tables created within a database reside on the Amazon S3 system,
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you can include an <codeph>s3a://</codeph> prefix on the <codeph>LOCATION</codeph>
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attribute. In <keyword keyref="impala26_full"/> and higher, Impala automatically creates any
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required folders as the databases, tables, and partitions are created, and removes
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them when they are dropped.
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</p>
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<p conref="../shared/impala_common.xml#common/s3_ddl"/>
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<p conref="../shared/impala_common.xml#common/cancel_blurb_no"/>
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<p conref="../shared/impala_common.xml#common/permissions_blurb"/>
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<p rev="CDH-19187">
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The user ID that the <cmdname>impalad</cmdname> daemon runs under,
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typically the <codeph>impala</codeph> user, must have write
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permission for the parent HDFS directory under which the database
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is located.
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</p>
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<p conref="../shared/impala_common.xml#common/example_blurb"/>
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<codeblock conref="../shared/impala_common.xml#common/create_drop_db_example"/>
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<p conref="../shared/impala_common.xml#common/related_info"/>
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<p>
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<xref href="impala_databases.xml#databases"/>, <xref href="impala_drop_database.xml#drop_database"/>,
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<xref href="impala_use.xml#use"/>, <xref href="impala_show.xml#show_databases"/>,
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<xref href="impala_tables.xml#tables"/>
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</p>
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</conbody>
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</concept>
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