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These are refugees from doc_prototype. They can be rendered with the DITA Open Toolkit version 2.3.3 by: /tmp/dita-ot-2.3.3/bin/dita \ -i impala.ditamap \ -f html5 \ -o $(mktemp -d) \ -filter impala_html.ditaval Change-Id: I8861e99adc446f659a04463ca78c79200669484f Reviewed-on: http://gerrit.cloudera.org:8080/5014 Reviewed-by: John Russell <jrussell@cloudera.com> Tested-by: John Russell <jrussell@cloudera.com>
58 lines
2.9 KiB
XML
58 lines
2.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
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<concept id="schema_objects">
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<title>Impala Schema Objects and Object Names</title>
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<titlealts audience="PDF"><navtitle>Schema Objects and Object Names</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="Data Analysts"/>
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<data name="Category" value="Developers"/>
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<data name="Category" value="Querying"/>
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<data name="Category" value="Schemas"/>
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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="Cloudera">schema objects</indexterm>
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With Impala, you work with schema objects that are familiar to database users: primarily databases, tables, views,
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and functions. The SQL syntax to work with these objects is explained in
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<xref href="impala_langref_sql.xml#langref_sql"/>. This section explains the conceptual knowledge you need to
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work with these objects and the various ways to specify their names.
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</p>
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<p>
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Within a table, partitions can also be considered a kind of object. Partitioning is an important subject for
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Impala, with its own documentation section covering use cases and performance considerations. See
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<xref href="impala_partitioning.xml#partitioning"/> for details.
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</p>
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<p>
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Impala does not have a counterpart of the <q>tablespace</q> notion from some database systems. By default,
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all the data files for a database, table, or partition are located within nested folders within the HDFS file
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system. You can also specify a particular HDFS location for a given Impala table or partition. The raw data
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for these objects is represented as a collection of data files, providing the flexibility to load data by
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simply moving files into the expected HDFS location.
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</p>
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<p>
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Information about the schema objects is held in the
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<xref href="impala_hadoop.xml#intro_metastore">metastore</xref> database. This database is shared between
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Impala and Hive, allowing each to create, drop, and query each other's databases, tables, and so on. When
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Impala makes a change to schema objects through a <codeph>CREATE</codeph>, <codeph>ALTER</codeph>,
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<codeph>DROP</codeph>, <codeph>INSERT</codeph>, or <codeph>LOAD DATA</codeph> statement, it broadcasts those
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changes to all nodes in the cluster through the <xref href="impala_components.xml#intro_catalogd">catalog
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service</xref>. When you make such changes through Hive or directly through manipulating HDFS files, you use
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the <xref href="impala_refresh.xml#refresh">REFRESH</xref> or
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<xref href="impala_invalidate_metadata.xml#invalidate_metadata">INVALIDATE METADATA</xref> statements on the
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Impala side to recognize the newly loaded data, new tables, and so on.
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</p>
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<p outputclass="toc"/>
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</conbody>
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</concept>
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