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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="num_scanner_threads">
<title>NUM_SCANNER_THREADS Query Option</title>
<titlealts audience="PDF"><navtitle>NUM_SCANNER_THREADS</navtitle></titlealts>
<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"/>
<indexterm audience="hidden">NUM_SCANNER_THREADS query option</indexterm>
Maximum number of scanner threads (on each node) used for each query. By default, Impala uses as many cores
as are available (one thread per core). You might lower this value if queries are using excessive resources
on a busy cluster. Impala imposes a maximum value automatically, so a high value has no practical effect.
<b>Type:</b> numeric
<b>Default:</b> 0