Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/21619#discussion_r197795127
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/javaCode.scala
---
@@ -148,14 +149,17 @@ trait Block extends JavaCode {
}
// Concatenates this block with other block.
- def + (other: Block): Block
+ def + (other: Block): Block = other match {
--- End diff --
A general question about `+`.
Previously we generate a giant string for an expression tree, which is hard
to tune. To keep more information in the generated code, we introduce this
`JavaCode`/`CodeBlock` framework to keep a tree of strings instead of a giant
string.
For an expression `a op b`, we should generate a tree of strings for `a`
and `b`, then `op` creates a new tree node and keeps `a` and `b` as children.
That means, if we refer to a `CodeBlock` inside a `code"..."`, the `CodeBlock`
should become a child of the new `CodeBlock`. However, `+` usually happens
within the same operator, I'm not sure if we should create a new level of tree
node here.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
