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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="kudu_read_mode" rev="3.1.0 IMPALA-6812">
<title>KUDU_READ_MODE Query Option (<keyword keyref="impala31"/> or higher only)</title>
<titlealts audience="PDF">
<data name="Category" value="Impala"/>
<data name="Category" value="Impala Query Options"/>
<data name="Category" value="Performance"/>
<data name="Category" value="Developers"/>
<data name="Category" value="Data Analysts"/>
<p rev="3.1.0 IMPALA-6812">
The <codeph>KUDU_READ_MODE</codeph> query option allows you to set a desired consistency
level for scans of Kudu tables.
<b>Type:</b> String
<b>Default:</b> <codeph>"DEFAULT"</codeph>
<b>Added in:</b> <keyword keyref="impala31"/>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
The following values are supported for the query option:
<codeph>"DEFAULT"</codeph>: The value of the startup flag,
<codeph>&#8209;&#8209;kudu_read_mode</codeph>, is used. </li>
<codeph>"READ_LATEST"</codeph>: Commonly known as the Read Committed isolation mode,
in this mode, Kudu provides no consistency guarantees for this mode, except that all
returned rows were committed at some point.
<codeph>"READ_AT_SNAPSHOT"</codeph>: Kudu will take a snapshot of the current state of
the data and perform the scan over the snapshot, possibly after briefly waiting for
ongoing writes to complete. This provides "Read Your Writes" consistency within a
single Impala session, except in the case of a Kudu leader change. See the Kudu
documentation for more details.