[SPARK-13766][SQL] Consistent file extensions for files written by internal data sources

## What changes were proposed in this pull request?

https://issues.apache.org/jira/browse/SPARK-13766
This PR makes the file extensions (written by internal datasource) consistent.

**Before**

- TEXT, CSV and JSON
```
[.COMPRESSION_CODEC_NAME]
```

- Parquet
```
[.COMPRESSION_CODEC_NAME].parquet
```

- ORC
```
.orc
```

**After**

- TEXT, CSV and JSON
```
.txt[.COMPRESSION_CODEC_NAME]
.csv[.COMPRESSION_CODEC_NAME]
.json[.COMPRESSION_CODEC_NAME]
```

- Parquet
```
[.COMPRESSION_CODEC_NAME].parquet
```

- ORC
```
[.COMPRESSION_CODEC_NAME].orc
```

When the compression codec is set,
- For Parquet and ORC, each still stays in Parquet and ORC format but just have compressed data internally. So, I think it is okay to name `.parquet` and `.orc` at the end.

- For Text, CSV and JSON, each does not stays in each format but it has different data format according to compression codec. So, each has the names `.json`, `.csv` and `.txt` before the compression extension.

## How was this patch tested?

Unit tests are used and `./dev/run_tests` for coding style tests.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #11604 from HyukjinKwon/SPARK-13766.

7 files changed, 12 insertions, 9 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVRelation.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVRelation.scala
index d7ce9a0ce8..0e6b9855c7 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVRelation.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVRelation.scala
@@ -140,7 +140,7 @@ private[sql] class CsvOutputWriter(
         val uniqueWriteJobId = configuration.get("spark.sql.sources.writeJobUUID")
         val taskAttemptId = context.getTaskAttemptID
         val split = taskAttemptId.getTaskID.getId
-        new Path(path, f"part-r-$split%05d-$uniqueWriteJobId$extension")
+        new Path(path, f"part-r-$split%05d-$uniqueWriteJobId.csv$extension")
       }
     }.getRecordWriter(context)
   }
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala
index 497e3c59e9..05b44d1a2a 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala
@@ -167,7 +167,7 @@ private[json] class JsonOutputWriter(
         val taskAttemptId = context.getTaskAttemptID
         val split = taskAttemptId.getTaskID.getId
         val bucketString = bucketId.map(BucketingUtils.bucketIdToString).getOrElse("")
-        new Path(path, f"part-r-$split%05d-$uniqueWriteJobId$bucketString$extension")
+        new Path(path, f"part-r-$split%05d-$uniqueWriteJobId$bucketString.json$extension")
       }
     }.getRecordWriter(context)
   }
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRelation.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRelation.scala
index 82404b8499..f1060074d6 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRelation.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRelation.scala
@@ -379,6 +379,9 @@ private[sql] class ParquetOutputWriter(
           val taskAttemptId = context.getTaskAttemptID
           val split = taskAttemptId.getTaskID.getId
           val bucketString = bucketId.map(BucketingUtils.bucketIdToString).getOrElse("")
+          // It has the `.parquet` extension at the end because (de)compression tools
+          // such as gunzip would not be able to decompress this as the compression
+          // is not applied on this whole file but on each "page" in Parquet format.
           new Path(path, f"part-r-$split%05d-$uniqueWriteJobId$bucketString$extension")
         }
       }
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/text/DefaultSource.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/text/DefaultSource.scala
index b3297254cb..2869a6a1ac 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/text/DefaultSource.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/text/DefaultSource.scala
@@ -140,7 +140,7 @@ class TextOutputWriter(path: String, dataSchema: StructType, context: TaskAttemp
         val uniqueWriteJobId = configuration.get("spark.sql.sources.writeJobUUID")
         val taskAttemptId = context.getTaskAttemptID
         val split = taskAttemptId.getTaskID.getId
-        new Path(path, f"part-r-$split%05d-$uniqueWriteJobId$extension")
+        new Path(path, f"part-r-$split%05d-$uniqueWriteJobId.txt$extension")
       }
     }.getRecordWriter(context)
   }
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVSuite.scala
index 076fe5e041..680759d457 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVSuite.scala
@@ -404,7 +404,7 @@ class CSVSuite extends QueryTest with SharedSQLContext with SQLTestUtils {
         .save(csvDir)
 
       val compressedFiles = new File(csvDir).listFiles()
-      assert(compressedFiles.exists(_.getName.endsWith(".gz")))
+      assert(compressedFiles.exists(_.getName.endsWith(".csv.gz")))
 
       val carsCopy = sqlContext.read
         .format("csv")
@@ -439,7 +439,7 @@ class CSVSuite extends QueryTest with SharedSQLContext with SQLTestUtils {
           .save(csvDir)
 
         val compressedFiles = new File(csvDir).listFiles()
-        assert(compressedFiles.exists(!_.getName.endsWith(".gz")))
+        assert(compressedFiles.exists(!_.getName.endsWith(".csv.gz")))
 
         val carsCopy = sqlContext.read
           .format("csv")
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala
index 02b173d30a..097ece3525 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala
@@ -1441,7 +1441,7 @@ class JsonSuite extends QueryTest with SharedSQLContext with TestJsonData {
         .save(jsonDir)
 
       val compressedFiles = new File(jsonDir).listFiles()
-      assert(compressedFiles.exists(_.getName.endsWith(".gz")))
+      assert(compressedFiles.exists(_.getName.endsWith(".json.gz")))
 
       val jsonCopy = sqlContext.read
         .format("json")
@@ -1479,7 +1479,7 @@ class JsonSuite extends QueryTest with SharedSQLContext with TestJsonData {
           .save(jsonDir)
 
         val compressedFiles = new File(jsonDir).listFiles()
-        assert(compressedFiles.exists(!_.getName.endsWith(".gz")))
+        assert(compressedFiles.exists(!_.getName.endsWith(".json.gz")))
 
         val jsonCopy = sqlContext.read
           .format("json")
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/text/TextSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/text/TextSuite.scala
index 9eb1016b64..ee398721c0 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/text/TextSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/text/TextSuite.scala
@@ -74,7 +74,7 @@ class TextSuite extends QueryTest with SharedSQLContext {
         val tempDirPath = tempDir.getAbsolutePath
         testDf.write.option("compression", codecName).mode(SaveMode.Overwrite).text(tempDirPath)
         val compressedFiles = new File(tempDirPath).listFiles()
-        assert(compressedFiles.exists(_.getName.endsWith(extension)))
+        assert(compressedFiles.exists(_.getName.endsWith(s".txt$extension")))
         verifyFrame(sqlContext.read.text(tempDirPath))
     }
 
@@ -102,7 +102,7 @@ class TextSuite extends QueryTest with SharedSQLContext {
         val tempDirPath = tempDir.getAbsolutePath
         testDf.write.option("compression", "none").mode(SaveMode.Overwrite).text(tempDirPath)
         val compressedFiles = new File(tempDirPath).listFiles()
-        assert(compressedFiles.exists(!_.getName.endsWith(".gz")))
+        assert(compressedFiles.exists(!_.getName.endsWith(".txt.gz")))
         verifyFrame(sqlContext.read.text(tempDirPath))
       } finally {
         // Hadoop 1 doesn't have `Configuration.unset`