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        <span>Presto 0.102 Documentation</span></a></h1>
    <h2 class="heading"><span>7.8. EXPLAIN</span></h2>
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  <div class="section" id="explain">
<h1>7.8. EXPLAIN</h1>
<div class="section" id="synopsis">
<h2>Synopsis</h2>
<div class="highlight-none"><div class="highlight"><pre>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>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]
                             regionkey := tpch:tpch:regionkey:2
</pre></div>
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<p>Distributed plan:</p>
<div class="highlight-none"><div class="highlight"><pre>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]
                 regionkey := tpch:tpch:regionkey:2
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