EXPLAIN

Se aplica a: Databricks SQL Databricks Runtime

Proporciona los planes lógicos o físicos de una instrucción de entrada. De manera predeterminada, esta cláusula proporciona información solo sobre un plan físico.

Sintaxis

EXPLAIN [ EXTENDED | CODEGEN | COST | FORMATTED ] statement

Parámetros

• EXTENDED

  Genera un plan lógico redistribuido, un plan lógico analizado, un plan lógico optimizado y un plan físico. El plan lógico redistribuido es un plan sin resolver extraído de la consulta. El plan lógico analizado se transforma, lo que convierte unresolvedAttribute y unresolvedRelation en objetos con tipo. El plan lógico optimizado se transforma a través de un conjunto de reglas de optimización, lo que da lugar al plan físico.

• CODEGEN

  Genera código para la instrucción, si la hay, y un plan físico.

• COST

  Si hay estadísticas de nodo de plan disponibles, genera un plan lógico y las estadísticas.

• FORMATTED

  Genera dos secciones: un esquema de plan físico y detalles de nodo.

• instrucción

  Instrucción SQL que se va a explicar.

Ejemplos

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