EXPLAIN

MySQL の標準結果形式に加えて、TiDB は DotGraph もサポートしており、次の例のようにFORMAT = "dot"を指定する必要があります。

CREATE TABLE t(a bigint, b bigint);
EXPLAIN format = "dot" SELECT A.a, B.b FROM t A JOIN t B ON A.a > B.b WHERE A.a < 10;

+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| dot contents                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|
digraph Projection_8 {
subgraph cluster8{
node [style=filled, color=lightgrey]
color=black
label = "root"
"Projection_8" -> "HashJoin_9"
"HashJoin_9" -> "TableReader_13"
"HashJoin_9" -> "Selection_14"
"Selection_14" -> "TableReader_17"
}
subgraph cluster12{
node [style=filled, color=lightgrey]
color=black
label = "cop"
"Selection_12" -> "TableFullScan_11"
}
subgraph cluster16{
node [style=filled, color=lightgrey]
color=black
label = "cop"
"Selection_16" -> "TableFullScan_15"
}
"TableReader_13" -> "Selection_12"
"TableReader_17" -> "Selection_16"
}
 |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

コンピュータにdotプログラムがある場合は、次の方法を使用して PNG ファイルを生成できます。

dot xx.dot -T png -O

The xx.dot is the result returned by the above statement.

コンピュータにdotプログラムがない場合は、結果をこのウェブサイトにコピーして樹形図を取得します。

JSON で出力を取得するには、 EXPLAINステートメントにFORMAT = "tidb_json"を指定します。以下は例です。

CREATE TABLE t(id int primary key, a int, b int, key(a));
EXPLAIN FORMAT = "tidb_json" SELECT id FROM t WHERE a = 1;

+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| TiDB_JSON                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| [
    {
        "id": "Projection_4",
        "estRows": "10.00",
        "taskType": "root",
        "operatorInfo": "test.t.id",
        "subOperators": [
            {
                "id": "IndexReader_6",
                "estRows": "10.00",
                "taskType": "root",
                "operatorInfo": "index:IndexRangeScan_5",
                "subOperators": [
                    {
                        "id": "IndexRangeScan_5",
                        "estRows": "10.00",
                        "taskType": "cop[tikv]",
                        "accessObject": "table:t, index:a(a)",
                        "operatorInfo": "range:[1,1], keep order:false, stats:pseudo"
                    }
                ]
            }
        ]
    }
]
 |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

出力では、 id 、 estRows 、 taskType 、 accessObject 、およびoperatorInfoは、デフォルト形式の列と同じ意味を持ちます。 subOperatorsはサブノードを格納する配列です。サブノードのフィールドと意味は親ノードと同じです。フィールドが欠落している場合は、そのフィールドが空であることを意味します。