Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/18581#discussion_r135381676
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/HadoopFileLinesReader.scala
---
@@ -32,7 +32,9 @@ import
org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl
* in that file.
*/
class HadoopFileLinesReader(
- file: PartitionedFile, conf: Configuration) extends Iterator[Text]
with Closeable {
+ file: PartitionedFile,
+ lineSeparator: Option[String],
--- End diff --
Thanks for clarifying it. Here is my investigation:
> When the line delimiter is '\n', any of the follow sequences will count
as a delimiter: "\n", "\r\n", or "\r"
With this input:
```
a\nb\r\nc\rd
```
Case with `\n`:
```sql
CREATE EXTERNAL TABlE tbl(value STRING)
ROW FORMAT DELIMITED LINES TERMINATED BY '\n'
STORED AS TEXTFILE LOCATION '...';
```
```sql
SELECT value FROM tbl;
```
produced
```
a
b
c
d
```
This looks incorrect. I _guess_ `\n` is not being set and it looks working
as the default behaviour in `LineRecordReader`.
> Accepting a single "\r" is pretty strange, but that's what Hive does so
we emulate this behavior.
Case with `\r`:
```sql
CREATE EXTERNAL TABlE tbl(value STRING)
ROW FORMAT DELIMITED LINES TERMINATED BY '\r'
STORED AS TEXTFILE LOCATION '...';
```
produced
```
FAILED: SemanticException 2:41 LINES TERMINATED BY only supports newline
'\n' right now. Error encountered near token ''\r''
...
org.apache.hadoop.hive.ql.parse.SemanticException: 2:41 LINES TERMINATED BY
only supports newline '\n' right now. Error encountered near token ''\r''
```
This looks related with https://issues.apache.org/jira/browse/HIVE-5999
and these lines:
https://github.com/apache/hive/blob/696be9f52dfc6fb59c24de19726b4460100fc9ba/ql/src/java/org/apache/hadoop/hive/ql/parse/BaseSemanticAnalyzer.java#L198-L203
if I am not mistaken.
I am curious how this case was tested in the JIRA. If this test used
`textinputformat.record.delimiter`, then, this seems Hadoop's property, which
is basically the same thing as what I am doing here.
> Is Hive using Hadoop's LineRecordReader?
In the case above, the input format was
`org.apache.hadoop.mapred.TextInputFormat`, which uses `LineRecordReader`.
> How does Hive support it?
It looks Hive tries to support it by `LINES TERMINATED BY '\r'`
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-CreateTableCreate/Drop/TruncateTable.
I could not find other (formal) ways.
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