解釋

  • 發行項

適用于：核取標示為是 Databricks SQL 檢查標示為是 Databricks Runtime

提供輸入語句的邏輯或實體計畫。 根據預設，這個子句只會提供實體計畫的相關資訊。

語法

EXPLAIN [ EXTENDED | CODEGEN | COST | FORMATTED ] statement

參數

  • 擴展

    產生剖析的邏輯計畫、分析的邏輯計畫、優化的邏輯計畫和實體計畫。 剖析的邏輯計畫是從查詢中擷取的未解析計畫。 分析的邏輯計畫會轉換，將未解析的Attribute 和 unresolvedRelation 轉譯成完全型別的物件。 優化邏輯計畫會透過一組優化規則來轉換，進而產生實體計畫。

  • CODEGEN

    如果有任何和實體計畫，則為 語句產生程式碼。

  • 成本

    如果有可用的計畫節點統計資料，則會產生邏輯計畫和統計資料。

  • 格式 化

    產生兩個區段：實體計畫大綱和節點詳細資料。

  • 聲明

    要說明的 SQL 語句。

例子

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