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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="s3_skip_insert_staging" rev="2.6.0 IMPALA-3452">
<title>S3_SKIP_INSERT_STAGING Query Option (<keyword keyref="impala26"/> or higher only)</title>
<titlealts audience="PDF"><navtitle>S3 SKIP INSERT STAGING</navtitle></titlealts>
<prolog>
<metadata>
<data name="Category" value="Impala"/>
<data name="Category" value="Impala Query Options"/>
<data name="Category" value="Amazon"/>
<data name="Category" value="S3"/>
<data name="Category" value="Performance"/>
<data name="Category" value="Developers"/>
<data name="Category" value="Data Analysts"/>
</metadata>
</prolog>
<conbody>
<p rev="2.6.0 IMPALA-3452">
<indexterm audience="hidden">IMPALA_S3_SKIP_INSERT_STAGING query option</indexterm>
</p>
<p>
Speeds up <codeph>INSERT</codeph> operations on tables or partitions residing on the
Amazon S3 filesystem. The tradeoff is the possibility of inconsistent data left behind
if an error occurs partway through the operation.
</p>
<p>
By default, Impala write operations to S3 tables and partitions involve a two-stage process.
Impala writes intermediate files to S3, then (because S3 does not provide a <q>rename</q>
operation) those intermediate files are copied to their final location, making the process
more expensive as on a filesystem that supports renaming or moving files.
This query option makes Impala skip the intermediate files, and instead write the
new data directly to the final destination.
</p>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
<note type="important">
<p>
If a host that is participating in the <codeph>INSERT</codeph> operation fails partway through
the query, you might be left with a table or partition that contains some but not all of the
expected data files. Therefore, this option is most appropriate for a development or test
environment where you have the ability to reconstruct the table if a problem during
<codeph>INSERT</codeph> leaves the data in an inconsistent state.
</p>
</note>
<p>
The timing of file deletion during an <codeph>INSERT OVERWRITE</codeph> operation
makes it impractical to write new files to S3 and delete the old files in a single operation.
Therefore, this query option only affects regular <codeph>INSERT</codeph> statements that add
to the existing data in a table, not <codeph>INSERT OVERWRITE</codeph> statements.
Use <codeph>TRUNCATE TABLE</codeph> if you need to remove all contents from an S3 table
before performing a fast <codeph>INSERT</codeph> with this option enabled.
</p>
<p>
Performance improvements with this option enabled can be substantial. The speed increase
might be more noticeable for non-partitioned tables than for partitioned tables.
</p>
<p conref="../shared/impala_common.xml#common/type_boolean"/>
<p conref="../shared/impala_common.xml#common/default_true_1"/>
<p conref="../shared/impala_common.xml#common/added_in_260"/>
<p conref="../shared/impala_common.xml#common/related_info"/>
<p>
<xref href="impala_s3.xml#s3"/>
</p>
</conbody>
</concept>