EqualNullSafe Predicate Expression¶

EqualNullSafe is a BinaryComparison predicate expression that represents the following high-level operators in a logical plan:

• <=> SQL operator
• Column.<=> operator

Null Safeness¶

EqualNullSafe is safe for null values, i.e. is like EqualTo with the following "safeness":

• true if both operands are null
• false if either operand is null

Creating Instance¶

EqualNullSafe takes the following to be created:

• Left Expression
• Right Expression

EqualNullSafe is created when:

• AstBuilder is requested to parse a comparison (for <=> operator) and withPredicate
• Column.<=> operator is used
• others

Symbol¶

symbol: String

symbol is part of the BinaryOperator abstraction.

symbol is <=>.

nullable¶

nullable: Boolean

nullable is part of the Expression abstraction.

nullable is always false.

Catalyst DSL¶

Catalyst DSL defines <=> operator to create an EqualNullSafe expression.

import org.apache.spark.sql.catalyst.dsl.expressions._
val right = 'right
val left = 'left
val e = right <=> left

scala> e.explain(extended = true)
('right <=> 'left)

scala> println(e.expr.sql)
(`right` <=> `left`)

import org.apache.spark.sql.catalyst.expressions.EqualNullSafe
assert(e.expr.isInstanceOf[EqualNullSafe])