Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/16680#discussion_r99583376
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVUtils.scala
---
@@ -0,0 +1,134 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.datasources.csv
+
+import org.apache.spark.sql.Dataset
+import org.apache.spark.sql.functions._
+import org.apache.spark.sql.types._
+
+object CSVUtils {
+ /**
+ * Filter ignorable rows for CSV dataset (lines empty and starting with
`comment`).
+ * This is currently being used in CSV schema inference.
+ */
+ def filterCommentAndEmpty(lines: Dataset[String], options: CSVOptions):
Dataset[String] = {
+ // Note that this was separately made by SPARK-18362. Logically, this
should be the same
+ // with the one below, `filterCommentAndEmpty` but execution path is
different. One of them
+ // might have to be removed in the near future if possible.
+ import lines.sqlContext.implicits._
+ val nonEmptyLines = lines.filter(length(trim($"value")) > 0)
+ if (options.isCommentSet) {
+ nonEmptyLines.filter(!$"value".startsWith(options.comment.toString))
+ } else {
+ nonEmptyLines
+ }
+ }
+
+ /**
+ * Filter ignorable rows for CSV iterator (lines empty and starting with
`comment`).
+ * This is currently being used in CSV reading path and CSV schema
inference.
+ */
+ def filterCommentAndEmpty(iter: Iterator[String], options: CSVOptions):
Iterator[String] = {
+ iter.filter { line =>
+ line.trim.nonEmpty && !line.startsWith(options.comment.toString)
+ }
+ }
+
+ /**
+ * Skip the given first line so that only data can remain in a dataset.
+ * This is similar with `dropHeaderLine` below and currently being used
in CSV schema inference.
+ */
+ def filterHeaderLine(
+ iter: Iterator[String],
+ firstLine: String,
+ options: CSVOptions): Iterator[String] = {
+ // Note that unlike actual CSV reading path, it simply filters the
given first line. Therefore,
+ // this skips the line same with the header if exists. One of them
might have to be removed
+ // in the near future if possible.
+ if (options.headerFlag) {
+ iter.filterNot(_ == firstLine)
+ } else {
+ iter
+ }
+ }
+
+ /**
+ * Drop header line so that only data can remain.
+ * This is similar with `filterHeaderLine` above and currently being
used in CSV reading path.
+ */
+ def dropHeaderLine(iter: Iterator[String], options: CSVOptions):
Iterator[String] = {
+ val nonEmptyLines = if (options.isCommentSet) {
+ val commentPrefix = options.comment.toString
+ iter.dropWhile { line =>
+ line.trim.isEmpty || line.trim.startsWith(commentPrefix)
+ }
+ } else {
+ iter.dropWhile(_.trim.isEmpty)
+ }
+
+ if (nonEmptyLines.hasNext) nonEmptyLines.drop(1)
+ iter
+ }
+
+ /**
+ * Helper method that converts string representation of a character to
actual character.
+ * It handles some Java escaped strings and throws exception if given
string is longer than one
+ * character.
+ */
+ @throws[IllegalArgumentException]
+ def toChar(str: String): Char = {
+ if (str.charAt(0) == '\\') {
+ str.charAt(1)
+ match {
+ case 't' => '\t'
+ case 'r' => '\r'
+ case 'b' => '\b'
+ case 'f' => '\f'
+ case '\"' => '\"' // In case user changes quote char and uses \"
as delimiter in options
+ case '\'' => '\''
+ case 'u' if str == """\u0000""" => '\u0000'
+ case _ =>
+ throw new IllegalArgumentException(s"Unsupported special
character for delimiter: $str")
+ }
+ } else if (str.length == 1) {
+ str.charAt(0)
+ } else {
+ throw new IllegalArgumentException(s"Delimiter cannot be more than
one character: $str")
+ }
+ }
+
+ /**
+ * Verify if the schema is supported in CSV datasource.
+ */
+ def verifySchema(schema: StructType): Unit = {
--- End diff --
This one resembled `JacksonUtils.verifySchema`.
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