com.twitter.scalding.parquet.tuple.macros.Macros.scala Maven / Gradle / Ivy

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package com.twitter.scalding.parquet.tuple.macros

import com.twitter.scalding.parquet.tuple.macros.impl.{ ParquetReadSupportProvider, ParquetSchemaProvider, WriteSupportProvider }
import com.twitter.scalding.parquet.tuple.scheme.{ ParquetReadSupport, ParquetWriteSupport }

import scala.language.experimental.macros

/**
 * Macros used to generate parquet tuple read/write support.
 * These macros support only case class that contains primitive fields or nested case classes and also collection fields
 * like scala List, Set, and Map.
 * @author Jian TANG
 */
object Macros {
  /**
   * Macro used to generate parquet schema for a given case class. For example if we have:
   *
   * case class SampleClassA(x: Int, y: String)
   * case class SampleClassB(a: SampleClassA, y: String)
   *
   * The macro will generate a parquet message type like this:
   *
   * """
   *   message SampleClassB {
   *     required group a {
   *       required int32 x;
   *       required binary y;
   *     }
   *     required binary y;
   *   }
   *  """
   *
   * @tparam T Case class type that contains primitive fields or collection fields or nested case class.
   * @return Generated case class parquet message type string
   */
  implicit def caseClassParquetSchema[T]: String = macro ParquetSchemaProvider.toParquetSchemaImpl[T]

  /**
   * Macro generated case class read support
   */
  implicit def caseClassParquetReadSupport[T]: ParquetReadSupport[T] = macro ParquetReadSupportProvider.toParquetReadSupportImpl[T]

  /**
   * Macro used to generate case class write support to parquet.
   * @tparam T User defined case class tuple type.
   * @return Generated case class tuple write support function.
   */
  implicit def caseClassParquetWriteSupport[T]: ParquetWriteSupport[T] = macro WriteSupportProvider.toWriteSupportImpl[T]
}