# EXPLAIN

### Description

The EXPLAIN statement is used to provide logical/physical plans for an input statement. By default, this clause provides information about a physical plan only.

### Syntax

EXPLAIN [ EXTENDED | CODEGEN | COST | FORMATTED ] statement


### Parameters

• EXTENDED

Generates parsed logical plan, analyzed logical plan, optimized logical plan and physical plan. Parsed Logical plan is a unresolved plan that extracted from the query. Analyzed logical plans transforms which translates unresolvedAttribute and unresolvedRelation into fully typed objects. The optimized logical plan transforms through a set of optimization rules, resulting in the physical plan.

• CODEGEN

Generates code for the statement, if any and a physical plan.

• COST

If plan node statistics are available, generates a logical plan and the statistics.

• FORMATTED

Generates two sections: a physical plan outline and node details.

• statement

Specifies a SQL statement to be explained.

### Examples

-- 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]
|
+----------------------------------------------------+