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        <span>Presto 0.157 Documentation</span></a></h1>
    <h2 class="heading"><span>8.14. EXPLAIN</span></h2>
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  <div class="section" id="explain">
<h1>8.14. EXPLAIN</h1>
<div class="section" id="synopsis">
<h2>Synopsis</h2>
<div class="highlight-none"><div class="highlight"><pre><span></span>EXPLAIN [ ( option [, ...] ) ] statement

where option can be one of:

    FORMAT { TEXT | GRAPHVIZ }
    TYPE { LOGICAL | DISTRIBUTED }
</pre></div>
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<div class="section" id="description">
<h2>Description</h2>
<p>Show the logical or distributed execution plan of a statement.</p>
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<div class="section" id="examples">
<h2>Examples</h2>
<p>Logical plan:</p>
<div class="highlight-none"><div class="highlight"><pre><span></span>presto:tiny&gt; EXPLAIN SELECT regionkey, count(*) FROM nation GROUP BY 1;
                                                Query Plan
----------------------------------------------------------------------------------------------------------
 - Output[regionkey, _col1] =&gt; [regionkey:bigint, count:bigint]
         _col1 := count
     - Exchange[GATHER] =&gt; regionkey:bigint, count:bigint
         - Aggregate(FINAL)[regionkey] =&gt; [regionkey:bigint, count:bigint]
                 count := &quot;count&quot;(&quot;count_8&quot;)
             - Exchange[REPARTITION] =&gt; regionkey:bigint, count_8:bigint
                 - Aggregate(PARTIAL)[regionkey] =&gt; [regionkey:bigint, count_8:bigint]
                         count_8 := &quot;count&quot;(*)
                     - TableScan[tpch:tpch:nation:sf0.01, original constraint=true] =&gt; [regionkey:bigint]
                             LAYOUT: tpch:nation:sf0.01
                             regionkey := tpch:regionkey
</pre></div>
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<p>Distributed plan:</p>
<div class="highlight-none"><div class="highlight"><pre><span></span>presto:tiny&gt; EXPLAIN (TYPE DISTRIBUTED) SELECT regionkey, count(*) FROM nation GROUP BY 1;
                                          Query Plan
----------------------------------------------------------------------------------------------
 Fragment 2 [SINGLE]
     Output layout: [regionkey, count]
     - Output[regionkey, _col1] =&gt; [regionkey:bigint, count:bigint]
             _col1 := count
         - RemoteSource[1] =&gt; [regionkey:bigint, count:bigint]

 Fragment 1 [FIXED]
     Output layout: [regionkey, count]
     - Aggregate(FINAL)[regionkey] =&gt; [regionkey:bigint, count:bigint]
             count := &quot;count&quot;(&quot;count_8&quot;)
         - RemoteSource[0] =&gt; [regionkey:bigint, count_8:bigint]

 Fragment 0 [SOURCE]
     Output layout: [regionkey, count_8]
     Output partitioning: [regionkey]
     - Aggregate(PARTIAL)[regionkey] =&gt; [regionkey:bigint, count_8:bigint]
             count_8 := &quot;count&quot;(*)
         - TableScan[tpch:tpch:nation:sf0.01, original constraint=true] =&gt; [regionkey:bigint]
                 LAYOUT: tpch:nation:sf0.01
                 regionkey := tpch:regionkey
</pre></div>
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<div class="section" id="see-also">
<h2>See Also</h2>
<p><a class="reference internal" href="explain-analyze.html"><span class="doc">EXPLAIN ANALYZE</span></a></p>
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