[GitHub] spark pull request #21193: [SPARK-24121][SQL] Add API for handling expressio...

[kiszk <gi...@git.apache.org>]

Github user kiszk commented on a diff in the pull request:

    https://github.com/apache/spark/pull/21193#discussion_r185995523
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/javaCode.scala ---
    @@ -112,6 +112,112 @@ object JavaCode {
       def isNullExpression(code: String): SimpleExprValue = {
         expression(code, BooleanType)
       }
    +
    +  def block(code: String): Block = {
    +    CodeBlock(codeParts = Seq(code), blockInputs = Seq.empty)
    +  }
    +}
    +
    +/**
    + * A trait representing a block of java code.
    + */
    +trait Block extends JavaCode {
    +
    +  // The expressions to be evaluated inside this block.
    +  def exprValues: Seq[ExprValue]
    +
    +  // This will be called during string interpolation.
    +  override def toString: String = _marginChar match {
    +    case Some(c) => code.stripMargin(c)
    +    case _ => code
    +  }
    +
    +  var _marginChar: Option[Char] = None
    +
    +  def stripMargin(c: Char): this.type = {
    +    _marginChar = Some(c)
    +    this
    +  }
    +
    +  def stripMargin: this.type = {
    +    _marginChar = Some('|')
    +    this
    +  }
    +
    +  def + (other: Block): Block
    +}
    +
    +object Block {
    +  implicit def blockToString(block: Block): String = block.toString
    +
    +  implicit def blocksToBlock(blocks: Seq[Block]): Block = Blocks(blocks)
    +
    +  implicit class BlockHelper(val sc: StringContext) extends AnyVal {
    +    def code(args: Any*): Block = {
    +      sc.checkLengths(args)
    +      if (sc.parts.length == 0) {
    +        EmptyBlock
    +      } else {
    +        args.foreach {
    +          case _: ExprValue =>
    +          case _: Int | _: Long | _: Float | _: Double | _: String =>
    +          case _: Block =>
    +          case other => throw new IllegalArgumentException(
    +            s"Can not interpolate ${other.getClass.getName} into code block.")
    +        }
    +        CodeBlock(sc.parts, args)
    +      }
    +    }
    +  }
    +}
    +
    +/**
    + * A block of java code. Including a sequence of code parts and some inputs to this block.
    + * The actual java code is generated by embedding the inputs into the code parts.
    + */
    +case class CodeBlock(codeParts: Seq[String], blockInputs: Seq[Any]) extends Block {
    +  override def exprValues: Seq[ExprValue] = {
    +    blockInputs.flatMap {
    +      case b: Block => b.exprValues
    +      case e: ExprValue => Seq(e)
    +      case _ => Seq.empty
    +    }
    +  }
    +
    +  override def code: String = {
    +    val strings = codeParts.iterator
    +    val inputs = blockInputs.iterator
    +    var buf = new StringBuffer(strings.next)
    +    while (strings.hasNext) {
    +      buf append inputs.next
    +      buf append strings.next
    +    }
    +    buf.toString
    +  }
    +
    +  override def + (other: Block): Block = other match {
    +    case c: CodeBlock => Blocks(Seq(this, c))
    +    case b: Blocks => Blocks(Seq(this) ++ b.blocks)
    +    case EmptyBlock => this
    +  }
    +}
    +
    +case class Blocks(blocks: Seq[Block]) extends Block {
    +  override def exprValues: Seq[ExprValue] = blocks.flatMap(_.exprValues)
    +  override def code: String = blocks.map(_.toString).mkString
    --- End diff --
    
    I am just curious whether `mkString` may lead to 64KB limit issue.


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