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Explain Analyze field description

The result output of the EXPLAIN ANALYZE statement can be shown in two forms: text and JSON. This article shows examples of output in both forms and introduces the meanings of the operators within them.

Text form

Example

│ Segment[0]                                                                                          │ 
│    Output Exchange: Output                                                                          │ 
│    Parallel Size: 1, Cluster Name: test_shard_localhost, Exchange Parallel Size: 1                  │ 
│    Output Columns: [a, t2.b]                                                                        │ 
│       Gather Exchange segment[1] Est. ? rows                                                        │ 
│                                                                                                     │ 
│ Segment[1]                                                                                          │ 
│    Output Exchange: GATHER                                                                          │ 
│    Parallel Size: 1, Cluster Name: test_shard_localhost, Exchange Parallel Size: 1                  │ 
│    Outputs: [( SegmentID:0 PlanSegmentType:EXCHANGE ParallelSize:1 ShuffleFunctionName:cityHash64)] │ 
│    Output Columns: [a, t2.b]                                                                        │ 
│       Projection Est. ? rows                                                                        │ 
│       │     Expressions: a:=a_1, t2.b:=b_2                                                          │ 
│       └─ Inner Join Est. ? rows                                                                     │ 
│          │     Condition: a_1 == a_2                                                                │ 
│          ├─ Buffer Est. ? rows                                                                      │ 
│          │  └─ CTERef[0] <-- segment[2] Est. ? rows                                                 │ 
│          └─ Buffer Est. ? rows                                                                      │ 
│             └─ CTERef[0] <-- segment[2] Est. ? rows                                                 │ 
│                                                                                                     │ 
│ Segment[2]                                                                                          │ 
│    Output Exchange: REPARTITION[a, a]                                                               │ 
│    Parallel Size: 1, Cluster Name: test_shard_localhost, Exchange Parallel Size: 1                  │ 
│    Outputs: [( SegmentID:1 PlanSegmentType:EXCHANGE ParallelSize:1 ShuffleFunctionName:cityHash64)  │ 
│              ( SegmentID:1 PlanSegmentType:EXCHANGE ParallelSize:1 ShuffleFunctionName:cityHash64)] │ 
│    Output Columns: [a, b]                                                                           │ 
│       TableScan test.t48028 Est. ? rows                                                             │ 
│             Outputs: [a, b]                                                                         │ 
│

Operator meanings

Output Exchange: The method by which the current segment outputs data, indicating how the data from the current segment is transmitted to the next segment. Supported forms include Output, LOCAL_NO_NEED_REPARTITION, LOCAL_MAY_NEED_REPARTITION, BROADCAST, REPARTITION, GATHER, and UNKNOWN. When the form is Repartition, the shuffle keys are displayed in the brackets following Repartition.
Output Columns: The column names output by the segment.
Outputs: Information about the output of the current segment's result to the next segment.
Parallel size: The degree of parallelism of the current segment.
Cluster Name: Cluster name
Exchange Parallel Size: Exchange parallel size.
Est.: Estimated information, based on statistical information: estimated rows and cost.
Act.: Actual execution information, which contains the following:
- output: Number of output rows, data size;
- wait time: Wait time when outputting data;
- Wall Time: Elapsed time for all operators;
- Input: Number of input rows, data size, wait time when inputting data.
QError: The ratio of the actual number of output rows from the operator to the estimated number of rows based on statistical information.
Filtered: The calculation formula is (maximum input rows - output rows) / maximum input rows
Where and Condition are both filter conditions.

JSON form

The JSON form omits statistical information.

Example

{ 
 "DistributedPlan" : [ 
  { 
   "SegmentID" : 2, 
   "OutputExchangeMode" : "REPARTITION", 
   "ShuffleKeys" : "REPARTITION", 
   "ParallelSize" : 1, 
   "ClusterName" : "test_shard_localhost", 
   "ExchangeParallelSize" : 1, 
   "OutputColumns" : [ 
    "a", 
    "b" 
   ], 
   "Outputs" : [ 
    { 
     "SegmentID" : 1, 
     "PlanSegmentType" : "EXCHANGE", 
     "ParallelSize" : 1, 
     "ShuffleFunctionName" : "cityHash64" 
    }, 
    { 
     "SegmentID" : 1, 
     "PlanSegmentType" : "EXCHANGE", 
     "ParallelSize" : 1, 
     "ShuffleFunctionName" : "cityHash64" 
    } 
   ], 
   "QueryPlan" : { 
    "NodeId" : 58, 
    "NodeType" : "TableScan", 
    "Outputs" : [ 
     "b", 
     "a" 
    ], 
    "Profiles" : { 
     "WallTimeMs" : 1, 
     "OutputRows" : 3, 
     "OutputBytes" : 24, 
     "OutputWaitTimeMs" : 0, 
     "Inputs" : [ 
      { 
       "InputNodeId" : -1, 
       "InputRows" : 0, 
       "InputBytes" : 0, 
       "InputWaitTimeMs" : 4 
      } 
     ], 
     "FilteredRate" : 0 
    } 
   } 
  }, 
  { 
   "SegmentID" : 1, 
   "OutputExchangeMode" : "GATHER", 
   "ParallelSize" : 1, 
   "ClusterName" : "test_shard_localhost", 
   "ExchangeParallelSize" : 1, 
   "OutputColumns" : [ 
    "a_1", 
    "a_2", 
    "b_2" 
   ], 
   "Outputs" : [ 
    { 
     "SegmentID" : 0, 
     "PlanSegmentType" : "EXCHANGE", 
     "ParallelSize" : 1, 
     "ShuffleFunctionName" : "cityHash64" 
    } 
   ], 
   "QueryPlan" : { 
    "NodeId" : 69, 
    "NodeType" : "Join", 
    "Strictness" : "", 
    "JoinKind" : "Inner", 
    "Condition" : [ 
     "a_1 == a_2" 
    ], 
    "Profiles" : { 
     "WallTimeMs" : 1, 
     "OutputRows" : 3, 
     "OutputBytes" : 36, 
     "OutputWaitTimeMs" : 0, 
     "Inputs" : [ 
      { 
       "InputNodeId" : 72, 
       "InputRows" : 3, 
       "InputBytes" : 12, 
       "InputWaitTimeMs" : 75 
      }, 
      { 
       "InputNodeId" : 73, 
       "InputRows" : 3, 
       "InputBytes" : 24, 
       "InputWaitTimeMs" : 72 
      } 
     ], 
     "FilteredRate" : 0 
    }, 
    "Children" : [ 
     { 
      "NodeId" : 72, 
      "NodeType" : "Buffer", 
      "Profiles" : { 
       "WallTimeMs" : 0, 
       "OutputRows" : 3, 
       "OutputBytes" : 12, 
       "OutputWaitTimeMs" : 40, 
       "Inputs" : [ 
        { 
         "InputNodeId" : 75, 
         "InputRows" : 3, 
         "InputBytes" : 12, 
         "InputWaitTimeMs" : 86 
        } 
       ], 
       "FilteredRate" : 0 
      }, 
      "Children" : [ 
       { 
        "NodeId" : 75, 
        "NodeType" : "Projection", 
        "Expressions" : [ 
         "a_1:=a" 
        ], 
        "Profiles" : { 
         "WallTimeMs" : 0, 
         "OutputRows" : 3, 
         "OutputBytes" : 12, 
         "OutputWaitTimeMs" : 0, 
         "Inputs" : [ 
          { 
           "InputNodeId" : 65, 
           "InputRows" : 3, 
           "InputBytes" : 24, 
           "InputWaitTimeMs" : 89 
          } 
         ], 
         "FilteredRate" : 0 
        }, 
        "Children" : [ 
         { 
          "NodeId" : 65, 
          "NodeType" : "RemoteExchangeSource", 
          "Segment[2]" : [ 
           "a", 
           "b" 
          ], 
          "Profiles" : { 
           "WallTimeMs" : 0, 
           "OutputRows" : 3, 
           "OutputBytes" : 24, 
           "OutputWaitTimeMs" : 5, 
           "Inputs" : [ 
            { 
             "InputNodeId" : -1, 
             "InputRows" : 0, 
             "InputBytes" : 0, 
             "InputWaitTimeMs" : 55 
            } 
           ], 
           "FilteredRate" : 0 
          } 
         } 
        ] 
       } 
      ] 
     }, 
     { 
      "NodeId" : 73, 
      "NodeType" : "Buffer", 
      "Profiles" : { 
       "WallTimeMs" : 0, 
       "OutputRows" : 3, 
       "OutputBytes" : 24, 
       "OutputWaitTimeMs" : 0, 
       "Inputs" : [ 
        { 
         "InputNodeId" : 76, 
         "InputRows" : 3, 
         "InputBytes" : 24, 
         "InputWaitTimeMs" : 74 
        } 
       ], 
       "FilteredRate" : 0 
      }, 
      "Children" : [ 
       { 
        "NodeId" : 76, 
        "NodeType" : "Projection", 
        "Expressions" : [ 
         "a_2:=a", 
         "b_2:=b" 
        ], 
        "Profiles" : { 
         "WallTimeMs" : 0, 
         "OutputRows" : 3, 
         "OutputBytes" : 24, 
         "OutputWaitTimeMs" : 0, 
         "Inputs" : [ 
          { 
           "InputNodeId" : 68, 
           "InputRows" : 3, 
           "InputBytes" : 24, 
           "InputWaitTimeMs" : 76 
          } 
         ], 
         "FilteredRate" : 0 
        }, 
        "Children" : [ 
         { 
          "NodeId" : 68, 
          "NodeType" : "RemoteExchangeSource", 
          "Segment[2]" : [ 
           "a", 
           "b" 
          ], 
          "Profiles" : { 
           "WallTimeMs" : 0, 
           "OutputRows" : 3, 
           "OutputBytes" : 24, 
           "OutputWaitTimeMs" : 5, 
           "Inputs" : [ 
            { 
             "InputNodeId" : -1, 
             "InputRows" : 0, 
             "InputBytes" : 0, 
             "InputWaitTimeMs" : 40 
            } 
           ], 
           "FilteredRate" : 0 
          } 
         } 
        ] 
       } 
      ] 
     } 
    ] 
   } 
  }, 
  { 
   "SegmentID" : 0, 
   "OutputExchangeMode" : "Output", 
   "ParallelSize" : 1, 
   "ClusterName" : "test_shard_localhost", 
   "ExchangeParallelSize" : 1, 
   "OutputColumns" : [ 
    "Explain Analyze" 
   ], 
   "QueryPlan" : { 
    "NodeId" : 71, 
    "NodeType" : "Projection", 
    "Expressions" : [ 
     "Explain Analyze" 
    ], 
    "Children" : [ 
     { 
      "NodeId" : 74, 
      "NodeType" : "ExplainAnalyze", 
      "Profiles" : { 
       "WallTimeMs" : 0, 
       "OutputRows" : 3, 
       "OutputBytes" : 36, 
       "OutputWaitTimeMs" : 0, 
       "Inputs" : [ 
        { 
         "InputNodeId" : 70, 
         "InputRows" : 3, 
         "InputBytes" : 36, 
         "InputWaitTimeMs" : 110 
        } 
       ], 
       "FilteredRate" : 0 
      }, 
      "Children" : [ 
       { 
        "NodeId" : 70, 
        "NodeType" : "RemoteExchangeSource", 
        "Segment[1]" : [ 
         "a_1", 
         "a_2", 
         "b_2" 
        ], 
        "Profiles" : { 
         "WallTimeMs" : 105, 
         "OutputRows" : 3, 
         "OutputBytes" : 36, 
         "OutputWaitTimeMs" : 0, 
         "Inputs" : [ 
          { 
           "InputNodeId" : -1, 
           "InputRows" : 0, 
           "InputBytes" : 0, 
           "InputWaitTimeMs" : 7 
          } 
         ], 
         "FilteredRate" : 0 
        } 
       } 
      ] 
     } 
    ] 
   } 
  } 
 ] 
}

Operator meanings

NodeId: The ID of the plan node.
NodeType: The type of the plan node.
Profiles: Profile information.

Last updated: 2026.03.31 16:13:52

ByteHouse Cloud Data Warehouse Version

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Example

Operator meanings

Example

Operator meanings