Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/6725#discussion_r32371138
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/math.scala
---
@@ -254,3 +254,52 @@ case class Pow(left: Expression, right: Expression)
"""
}
}
+
+object Logarithm {
+ def apply(child: Expression): Expression = new Log(child)
+}
+
+case class Logarithm(left: Expression, right: Expression)
+ extends BinaryMathExpression((c1, c2) => math.log(c2) / math.log(c1),
"LOG") {
--- End diff --
I think `BinaryArithmetic` is more limited in its semantic meaning. As I
can tell, it is more suitable for the binary expression between two expressions
of same type. `BinaryMathExpression` is more like to represent math function
with two expressions.
Due to support the case when the left is null in that 10 base logarithm is
applied, to override `eval()` is needed here.
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