scala> sql("SELECT current_database() AS database").show
...
TRACE SparkOptimizer:
=== Applying Rule org.apache.spark.sql.catalyst.optimizer.GetCurrentDatabase ===
GlobalLimit 21 GlobalLimit 21
+- LocalLimit 21 +- LocalLimit 21
! +- Project [currentdatabase() AS database#20] +- Project [default AS database#20]
+- OneRowRelation$ +- OneRowRelation$
...
+--------+
|database|
+--------+
| default|
+--------+GetCurrentDatabase and ComputeCurrentTime Logical Plan Optimizations
GetCurrentDatabase and ComputeCurrentTime optimization rules are part of Finish Analysis batch in the base Optimizer.
GetCurrentDatabase Optimization Rule
GetCurrentDatabase optimization rule returns the current database for current_database SQL function.
|
Note
|
You can access the current database in Scala using |
ComputeCurrentTime Optimization Rule
ComputeCurrentTime logical plan optimization rule computes the current date and timestamp.
scala> spark.range(1).select(current_date()).explain
...
TRACE SparkOptimizer:
=== Applying Rule org.apache.spark.sql.catalyst.optimizer.ComputeCurrentTime ===
!Project [current_date() AS current_date()#29] Project [17055 AS current_date()#29]
+- Range (0, 1, step=1, splits=Some(8)) +- Range (0, 1, step=1, splits=Some(8))scala> spark.range(1).select(current_timestamp()).explain
...
TRACE SparkOptimizer:
=== Applying Rule org.apache.spark.sql.catalyst.optimizer.ComputeCurrentTime ===
!Project [current_timestamp() AS current_timestamp()#36] Project [1473599927969000 AS current_timestamp()#36]
+- Range (0, 1, step=1, splits=Some(8)) +- Range (0, 1, step=1, splits=Some(8))