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<h1 id="sql-explain--page-root">EXPLAIN<a class="headerlink" href="#sql-explain--page-root" title="Permalink to this headline">#</a></h1>

<h2 id="synopsis">Synopsis<a class="headerlink" href="#synopsis" title="Permalink to this headline">#</a></h2>
<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>EXPLAIN [ ( option [, ...] ) ] statement

where option can be one of:

    FORMAT { TEXT | GRAPHVIZ | JSON }
    TYPE { LOGICAL | DISTRIBUTED | VALIDATE | IO }
</pre></div>
</div>


<h2 id="description">Description<a class="headerlink" href="#description" title="Permalink to this headline">#</a></h2>
<p>Show the logical or distributed execution plan of a statement, or validate the statement.
The distributed plan is shown by default. Each plan fragment of the distributed plan is executed by
a single or multiple Trino nodes. Fragments separation represent the data exchange between Trino nodes.
Fragment type specifies how the fragment is executed by Trino nodes and how the data is
distributed between fragments:</p>
<dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">SINGLE</span></code></dt><dd><p>Fragment is executed on a single node.</p>
</dd>
<dt><code class="docutils literal notranslate"><span class="pre">HASH</span></code></dt><dd><p>Fragment is executed on a fixed number of nodes with the input data
distributed using a hash function.</p>
</dd>
<dt><code class="docutils literal notranslate"><span class="pre">ROUND_ROBIN</span></code></dt><dd><p>Fragment is executed on a fixed number of nodes with the input data
distributed in a round-robin fashion.</p>
</dd>
<dt><code class="docutils literal notranslate"><span class="pre">BROADCAST</span></code></dt><dd><p>Fragment is executed on a fixed number of nodes with the input data
broadcasted to all nodes.</p>
</dd>
<dt><code class="docutils literal notranslate"><span class="pre">SOURCE</span></code></dt><dd><p>Fragment is executed on nodes where input splits are accessed.</p>
</dd>
</dl>


<h2 id="examples">Examples<a class="headerlink" href="#examples" title="Permalink to this headline">#</a></h2>

<h3 id="explain-type-logical">EXPLAIN (TYPE LOGICAL)<a class="headerlink" href="#explain-type-logical" title="Permalink to this headline">#</a></h3>
<p>Logical plan:</p>
<div class="highlight-sql notranslate"><div class="highlight"><pre><span></span><span class="k">EXPLAIN</span> <span class="p">(</span><span class="k">TYPE</span> <span class="n">LOGICAL</span><span class="p">)</span> <span class="k">SELECT</span> <span class="n">regionkey</span><span class="p">,</span> <span class="k">count</span><span class="p">(</span><span class="o">*</span><span class="p">)</span> <span class="k">FROM</span> <span class="n">nation</span> <span class="k">GROUP</span> <span class="k">BY</span> <span class="mi">1</span><span class="p">;</span>
</pre></div>
</div>
<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>                                                   Query Plan
-----------------------------------------------------------------------------------------------------------------
 Output[regionkey, _col1]
 │   Layout: [regionkey:bigint, count:bigint]
 │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
 │   _col1 := count
 └─ RemoteExchange[GATHER]
    │   Layout: [regionkey:bigint, count:bigint]
    │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
    └─ Aggregate(FINAL)[regionkey]
       │   Layout: [regionkey:bigint, count:bigint]
       │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
       │   count := count("count_8")
       └─ LocalExchange[HASH][$hashvalue] ("regionkey")
          │   Layout: [regionkey:bigint, count_8:bigint, $hashvalue:bigint]
          │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
          └─ RemoteExchange[REPARTITION][$hashvalue_9]
             │   Layout: [regionkey:bigint, count_8:bigint, $hashvalue_9:bigint]
             │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
             └─ Project[]
                │   Layout: [regionkey:bigint, count_8:bigint, $hashvalue_10:bigint]
                │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
                │   $hashvalue_10 := "combine_hash"(bigint '0', COALESCE("$operator$hash_code"("regionkey"), 0))
                └─ Aggregate(PARTIAL)[regionkey]
                   │   Layout: [regionkey:bigint, count_8:bigint]
                   │   count_8 := count(*)
                   └─ TableScan[tpch:nation:sf0.01]
                          Layout: [regionkey:bigint]
                          Estimates: {rows: 25 (225B), cpu: 225, memory: 0B, network: 0B}
                          regionkey := tpch:regionkey
</pre></div>
</div>


<h3 id="explain-type-distributed">EXPLAIN (TYPE DISTRIBUTED)<a class="headerlink" href="#explain-type-distributed" title="Permalink to this headline">#</a></h3>
<p>Distributed plan:</p>
<div class="highlight-sql notranslate"><div class="highlight"><pre><span></span><span class="k">EXPLAIN</span> <span class="p">(</span><span class="k">TYPE</span> <span class="n">DISTRIBUTED</span><span class="p">)</span> <span class="k">SELECT</span> <span class="n">regionkey</span><span class="p">,</span> <span class="k">count</span><span class="p">(</span><span class="o">*</span><span class="p">)</span> <span class="k">FROM</span> <span class="n">nation</span> <span class="k">GROUP</span> <span class="k">BY</span> <span class="mi">1</span><span class="p">;</span>
</pre></div>
</div>
<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>                                              Query Plan
------------------------------------------------------------------------------------------------------
 Fragment 0 [SINGLE]
     Output layout: [regionkey, count]
     Output partitioning: SINGLE []
     Stage Execution Strategy: UNGROUPED_EXECUTION
     Output[regionkey, _col1]
     │   Layout: [regionkey:bigint, count:bigint]
     │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
     │   _col1 := count
     └─ RemoteSource[1]
            Layout: [regionkey:bigint, count:bigint]

 Fragment 1 [HASH]
     Output layout: [regionkey, count]
     Output partitioning: SINGLE []
     Stage Execution Strategy: UNGROUPED_EXECUTION
     Aggregate(FINAL)[regionkey]
     │   Layout: [regionkey:bigint, count:bigint]
     │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
     │   count := count("count_8")
     └─ LocalExchange[HASH][$hashvalue] ("regionkey")
        │   Layout: [regionkey:bigint, count_8:bigint, $hashvalue:bigint]
        │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
        └─ RemoteSource[2]
               Layout: [regionkey:bigint, count_8:bigint, $hashvalue_9:bigint]

 Fragment 2 [SOURCE]
     Output layout: [regionkey, count_8, $hashvalue_10]
     Output partitioning: HASH [regionkey][$hashvalue_10]
     Stage Execution Strategy: UNGROUPED_EXECUTION
     Project[]
     │   Layout: [regionkey:bigint, count_8:bigint, $hashvalue_10:bigint]
     │   Estimates: {rows: ? (?), cpu: ?, memory: ?, network: ?}
     │   $hashvalue_10 := "combine_hash"(bigint '0', COALESCE("$operator$hash_code"("regionkey"), 0))
     └─ Aggregate(PARTIAL)[regionkey]
        │   Layout: [regionkey:bigint, count_8:bigint]
        │   count_8 := count(*)
        └─ TableScan[tpch:nation:sf0.01, grouped = false]
               Layout: [regionkey:bigint]
               Estimates: {rows: 25 (225B), cpu: 225, memory: 0B, network: 0B}
               regionkey := tpch:regionkey
</pre></div>
</div>


<h3 id="explain-type-validate">EXPLAIN (TYPE VALIDATE)<a class="headerlink" href="#explain-type-validate" title="Permalink to this headline">#</a></h3>
<p>Validate:</p>
<div class="highlight-sql notranslate"><div class="highlight"><pre><span></span><span class="k">EXPLAIN</span> <span class="p">(</span><span class="k">TYPE</span> <span class="n">VALIDATE</span><span class="p">)</span> <span class="k">SELECT</span> <span class="n">regionkey</span><span class="p">,</span> <span class="k">count</span><span class="p">(</span><span class="o">*</span><span class="p">)</span> <span class="k">FROM</span> <span class="n">nation</span> <span class="k">GROUP</span> <span class="k">BY</span> <span class="mi">1</span><span class="p">;</span>
</pre></div>
</div>
<div class="highlight-text notranslate"><div class="highlight"><pre><span></span> Valid
-------
 true
</pre></div>
</div>


<h3 id="explain-type-io">EXPLAIN (TYPE IO)<a class="headerlink" href="#explain-type-io" title="Permalink to this headline">#</a></h3>
<p>IO:</p>
<div class="highlight-sql notranslate"><div class="highlight"><pre><span></span><span class="k">EXPLAIN</span> <span class="p">(</span><span class="k">TYPE</span> <span class="n">IO</span><span class="p">,</span> <span class="n">FORMAT</span> <span class="n">JSON</span><span class="p">)</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">test_lineitem</span>
<span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">lineitem</span> <span class="k">WHERE</span> <span class="n">shipdate</span> <span class="o">=</span> <span class="s1">'2020-02-01'</span> <span class="k">AND</span> <span class="n">quantity</span> <span class="o">&gt;</span> <span class="mi">10</span><span class="p">;</span>
</pre></div>
</div>
<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>            Query Plan
-----------------------------------
{
   inputTableColumnInfos: [
      {
         table: {
            catalog: "hive",
            schemaTable: {
               schema: "tpch",
               table: "test_orders"
            }
         },
         columnConstraints: [
            {
               columnName: "orderkey",
               type: "bigint",
               domain: {
                  nullsAllowed: false,
                  ranges: [
                     {
                        low: {
                           value: "1",
                           bound: "EXACTLY"
                        },
                        high: {
                           value: "1",
                           bound: "EXACTLY"
                        }
                     },
                     {
                        low: {
                           value: "2",
                           bound: "EXACTLY"
                        },
                        high: {
                           value: "2",
                           bound: "EXACTLY"
                        }
                     }
                  ]
               }
            },
            {
               columnName: "processing",
               type: "boolean",
               domain: {
                  nullsAllowed: false,
                  ranges: [
                     {
                        low: {
                           value: "false",
                           bound: "EXACTLY"
                        },
                        high: {
                           value: "false",
                           bound: "EXACTLY"
                        }
                     }
                  ]
               }
            },
            {
               columnName: "custkey",
               type: "bigint",
               domain: {
                  nullsAllowed: false,
                  ranges: [
                     {
                        low: {
                           bound: "ABOVE"
                        },
                        high: {
                           value: "10",
                           bound: "EXACTLY"
                        }
                     }
                  ]
               }
            }
         ],
         estimate: {
            outputRowCount: 2,
            outputSizeInBytes: 40,
            cpuCost: 40,
            maxMemory: 0,
            networkCost: 0
         }
      }
   ],
   outputTable: {
      catalog: "hive",
      schemaTable: {
         schema: "tpch",
         table: "test_orders"
      }
   },
   estimate: {
      outputRowCount: "NaN",
      outputSizeInBytes: "NaN",
      cpuCost: "NaN",
      maxMemory: "NaN",
      networkCost: "NaN"
   }
}
</pre></div>
</div>


<h2 id="see-also">See also<a class="headerlink" href="#see-also" title="Permalink to this headline">#</a></h2>
<p><a class="reference internal" href="explain-analyze.html"><span class="doc">EXPLAIN ANALYZE</span></a></p>


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