Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/6660#discussion_r31858254
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
---
@@ -52,6 +53,45 @@ abstract class Expression extends TreeNode[Expression] {
def eval(input: Row = null): Any
/**
+ * Returns an [[GeneratedExpressionCode]], which contains Java source
code that
+ * can be used to generate the result of evaluating the expression on an
input row.
+ *
+ * @param ctx a [[CodeGenContext]]
+ * @return [[GeneratedExpressionCode]]
+ */
+ def gen(ctx: CodeGenContext): GeneratedExpressionCode = {
+ val nullTerm = ctx.freshName("nullTerm")
+ val primitiveTerm = ctx.freshName("primitiveTerm")
+ val ve = GeneratedExpressionCode("", nullTerm, primitiveTerm)
+ ve.code = genCode(ctx, ve)
+ ve
+ }
+
+ /**
+ * Returns Java source code that can be compiled to evaluate this
expression.
+ * The default behavior is to call the eval method of the expression.
Concrete expression
+ * implementations should override this to do actual code generation.
+ *
+ * @param ctx a [[CodeGenContext]]
+ * @param ev an [[GeneratedExpressionCode]] with unique terms.
+ * @return Java source code
+ */
+ protected def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode):
Code = {
+ val e = this.asInstanceOf[Expression]
--- End diff --
Why do we need this cast?
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