docs/build/plain-html/topics/impala_kudu_read_mode.html - impala - Git at Google

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   <h1 class="title topictitle1" id="ariaid-title1">KUDU_READ_MODE Query Option (<span class="keyword">Impala 3.1</span> or higher only)</h1>


   <div class="body conbody">

     <p class="p">
       The <code class="ph codeph">KUDU_READ_MODE</code> query option allows you to set a desired consistency
       level for scans of Kudu tables.
     </p>


     <p class="p">
       <strong class="ph b">Type:</strong> String
     </p>


     <p class="p">
       <strong class="ph b">Default:</strong> <code class="ph codeph">"DEFAULT"</code>
     </p>


     <p class="p">
       <strong class="ph b">Added in:</strong> <span class="keyword">Impala 3.1</span>
     </p>


     <p class="p">
         <strong class="ph b">Usage notes:</strong>
       </p>


     <div class="p">
       The following values are supported for the query option:
       <ul class="ul">
         <li class="li">
           <code class="ph codeph">"DEFAULT"</code>: The value of the startup flag,
             <code class="ph codeph">‑‑kudu_read_mode</code>, is used. </li>


         <li class="li">
           <code class="ph codeph">"READ_LATEST"</code>: 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.
         </li>


         <li class="li">
           <code class="ph codeph">"READ_AT_SNAPSHOT"</code>: 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.
         </li>

       </ul>

     </div>


   </div>


 <div class="related-links">
 <div class="familylinks">
 <div class="parentlink"><strong>Parent topic:</strong> <a class="link" href="../topics/impala_query_options.html">Query Options for the SET Statement</a></div>
 </div>
 </div></body>
 </html>
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	<title>KUDU_READ_MODE Query Option (Impala 3.1 or higher only)</title>
	</head>
	<body id="kudu_read_mode">


	<h1 class="title topictitle1" id="ariaid-title1">KUDU_READ_MODE Query Option (<span class="keyword">Impala 3.1</span> or higher only)</h1>






	<div class="body conbody">

	<p class="p">
	The <code class="ph codeph">KUDU_READ_MODE</code> query option allows you to set a desired consistency
	level for scans of Kudu tables.
	</p>


	<p class="p">
	<strong class="ph b">Type:</strong> String
	</p>


	<p class="p">
	<strong class="ph b">Default:</strong> <code class="ph codeph">"DEFAULT"</code>
	</p>


	<p class="p">
	<strong class="ph b">Added in:</strong> <span class="keyword">Impala 3.1</span>
	</p>


	<p class="p">
	<strong class="ph b">Usage notes:</strong>
	</p>


	<div class="p">
	The following values are supported for the query option:
	<ul class="ul">
	<li class="li">
	<code class="ph codeph">"DEFAULT"</code>: The value of the startup flag,
	<code class="ph codeph">‑‑kudu_read_mode</code>, is used. </li>


	<li class="li">
	<code class="ph codeph">"READ_LATEST"</code>: 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.
	</li>


	<li class="li">
	<code class="ph codeph">"READ_AT_SNAPSHOT"</code>: 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.
	</li>

	</ul>

	</div>


	</div>


	<div class="related-links">
	<div class="familylinks">
	<div class="parentlink"><strong>Parent topic:</strong> <a class="link" href="../topics/impala_query_options.html">Query Options for the SET Statement</a></div>
	</div>
	</div></body>
	</html>