# EXPLAIN

## 语法

``````EXPLAIN [ EXTENDED | CODEGEN | COST | FORMATTED ] statement
``````

## 参数

• EXTENDED

生成解析逻辑计划、分析逻辑计划、优化逻辑计划和物理计划。 解析逻辑计划是从查询中提取的未解析的计划。 分析型逻辑计划转换可将 unresolvedAttribute 和 unresolvedRelation 转换为完全类型化的对象。 优化型逻辑计划通过一组优化规则进行转换，从而生成物理计划。

• CODEGEN

为语句（如果有）和物理计划生成代码。

• COST

如果计划节点统计信息可用，则将生成逻辑计划和统计信息。

• FORMATTED

生成两个部分：物理计划概述和节点详细信息。

• 语句

要说明的 SQL 语句。

## 示例

``````-- Default Output
EXPLAIN select k, sum(v) from values (1, 2), (1, 3) t(k, v) group by k;
``````
``````+----------------------------------------------------+
|                                                plan|
+----------------------------------------------------+
| == Physical Plan ==
*(2) HashAggregate(keys=[k#33], functions=[sum(cast(v#34 as bigint))])
+- Exchange hashpartitioning(k#33, 200), true, [id=#59]
+- *(1) HashAggregate(keys=[k#33], functions=[partial_sum(cast(v#34 as bigint))])
+- *(1) LocalTableScan [k#33, v#34]
|
+----------------------------------------------------

-- Using Extended
``````
``````EXPLAIN EXTENDED select k, sum(v) from values (1, 2), (1, 3) t(k, v) group by k;
``````
``````+----------------------------------------------------+
|                                                plan|
+----------------------------------------------------+
| == Parsed Logical Plan ==
'Aggregate ['k], ['k, unresolvedalias('sum('v), None)]
+- 'SubqueryAlias `t`
+- 'UnresolvedInlineTable [k, v], [List(1, 2), List(1, 3)]

== Analyzed Logical Plan ==
k: int, sum(v): bigint
Aggregate [k#47], [k#47, sum(cast(v#48 as bigint)) AS sum(v)#50L]
+- SubqueryAlias `t`
+- LocalRelation [k#47, v#48]

== Optimized Logical Plan ==
Aggregate [k#47], [k#47, sum(cast(v#48 as bigint)) AS sum(v)#50L]
+- LocalRelation [k#47, v#48]

== Physical Plan ==
*(2) HashAggregate(keys=[k#47], functions=[sum(cast(v#48 as bigint))], output=[k#47, sum(v)#50L])
+- Exchange hashpartitioning(k#47, 200), true, [id=#79]
+- *(1) HashAggregate(keys=[k#47], functions=[partial_sum(cast(v#48 as bigint))], output=[k#47, sum#52L])
+- *(1) LocalTableScan [k#47, v#48]
|
+----------------------------------------------------+

-- Using Formatted
``````
``````EXPLAIN FORMATTED select k, sum(v) from values (1, 2), (1, 3) t(k, v) group by k;
``````
``````+----------------------------------------------------+
|                                                plan|
+----------------------------------------------------+
| == Physical Plan ==
* HashAggregate (4)
+- Exchange (3)
+- * HashAggregate (2)
+- * LocalTableScan (1)

(1) LocalTableScan [codegen id : 1]
Output: [k#19, v#20]

(2) HashAggregate [codegen id : 1]
Input: [k#19, v#20]

(3) Exchange
Input: [k#19, sum#24L]

(4) HashAggregate [codegen id : 2]
Input: [k#19, sum#24L]
|
+----------------------------------------------------+
``````