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<h1 class="title topictitle1" id="ariaid-title1">DISABLE_HBASE_NUM_ROWS_ESTIMATE Query Option</h1>
<div class="body conbody">
<p class="p">
Use the <code class="ph codeph">DISABLE_HBASE_NUM_ROWS_ESTIMATE</code> query option to disable key
sampling of HBase tables in row count and row size estimation.
</p>
<p class="p">
While generating a plan for an HBase query, the planner samples the underlying HBase
tables to estimate their row count and row size, and the sampling can negatively impact
the planning time. When the HBase table stats does not change much in short time, disable
the sampling by setting the <code class="ph codeph">DISABLE_HBASE_NUM_ROWS_ESTIMATE</code> query option
to <code class="ph codeph">TRUE</code>. And Impala planner will fall back to using Hive Metastore (HMS)
table stats instead.
</p>
<p class="p">
When <code class="ph codeph">DISABLE_HBASE_NUM_ROWS_ESTIMATE</code> query option is set to
<code class="ph codeph">TRUE</code>, you need to update the HMS table stats by running <code class="ph codeph">COMPUTE
STATS</code>. Alternatively, you can manually set table statistics by running
<code class="ph codeph">ALTER TABLE</code>. See <a class="xref" href="impala_perf_stats.html#perf_stats">Table and Column Statistics</a>
for details.
</p>
<div class="p">
The following values are supported:
<ul class="ul">
<li class="li">
<code class="ph codeph">TRUE</code> or <code class="ph codeph">1</code>: Disables the normal key sampling of HBase
tables and uses HMS table stats for estimation.
</li>
<li class="li">
<code class="ph codeph">FALSE</code> or <code class="ph codeph">0</code>: Enables the normal sampling of HBase
tables.
</li>
</ul>
</div>
<p class="p">
<strong class="ph b">Type:</strong> <code class="ph codeph">BOOLEAN</code>
</p>
<p class="p">
<strong class="ph b">Default:</strong> <code class="ph codeph">FALSE</code>
</p>
</div>
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