Github user squito commented on a diff in the pull request: https://github.com/apache/spark/pull/4187#discussion_r23501217 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetConverter.scala --- @@ -426,6 +423,33 @@ private[parquet] class CatalystPrimitiveConverter( parent.updateLong(fieldIndex, value) } +/** + * A `parquet.io.api.PrimitiveConverter` that converts Parquet Binary to Catalyst String. + * Supports dictionaries to reduce Binary to String conversion overhead. + * + * Follows pattern in Parquet of using dictionaries, where supported, for String conversion. + * + * @param parent The parent group converter. + * @param fieldIndex The index inside the record. + */ +private[parquet] class CatalystPrimitiveStringConverter(parent: CatalystConverter, fieldIndex: Int) + extends CatalystPrimitiveConverter(parent, fieldIndex) { + + private var dict: Array[String] = null + + override def hasDictionarySupport: Boolean = true + + override def setDictionary(dictionary: Dictionary):Unit = + dict = (for (i <- 0 to dictionary.getMaxId) --- End diff -- random esoteric scala detail: `foreach` on a `Range` is actually just about as good as a while loop. this **only** applies to `Range`, though, nothing else. more [here](https://github.com/scala/scala/commit/4cfc633fc6). I stumbled upon this a while back, if you are interested in reading more: http://imranrashid.com/posts/scala-loop-profiling/
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