Use single file write when an extension is present in the path.

datafusion/core/src/datasource/file_format/parquet.rs

@@ -2246,47 +2246,7 @@ mod tests {
 
     #[tokio::test]
     async fn parquet_sink_write() -> Result<()> {
-        let field_a = Field::new("a", DataType::Utf8, false);
-        let field_b = Field::new("b", DataType::Utf8, false);
-        let schema = Arc::new(Schema::new(vec![field_a, field_b]));
-        let object_store_url = ObjectStoreUrl::local_filesystem();
-
-        let file_sink_config = FileSinkConfig {
-            object_store_url: object_store_url.clone(),
-            file_groups: vec![PartitionedFile::new("/tmp".to_string(), 1)],
-            table_paths: vec![ListingTableUrl::parse("file:///")?],
-            output_schema: schema.clone(),
-            table_partition_cols: vec![],
-            insert_op: InsertOp::Overwrite,
-            keep_partition_by_columns: false,
-        };
-        let parquet_sink = Arc::new(ParquetSink::new(
-            file_sink_config,
-            TableParquetOptions {
-                key_value_metadata: std::collections::HashMap::from([
-                    ("my-data".to_string(), Some("stuff".to_string())),
-                    ("my-data-bool-key".to_string(), None),
-                ]),
-                ..Default::default()
-            },
-        ));
-
-        // create data
-        let col_a: ArrayRef = Arc::new(StringArray::from(vec!["foo", "bar"]));
-        let col_b: ArrayRef = Arc::new(StringArray::from(vec!["baz", "baz"]));
-        let batch = RecordBatch::try_from_iter(vec![("a", col_a), ("b", col_b)]).unwrap();
-
-        // write stream
-        parquet_sink
-            .write_all(
-                Box::pin(RecordBatchStreamAdapter::new(
-                    schema,
-                    futures::stream::iter(vec![Ok(batch)]),
-                )),
-                &build_ctx(object_store_url.as_ref()),
-            )
-            .await
-            .unwrap();
+        let parquet_sink = create_written_parquet_sink("file:///").await?;
 
         // assert written
         let mut written = parquet_sink.written();
@@ -2338,6 +2298,140 @@ mod tests {
         Ok(())
     }
 
+    #[tokio::test]
+    async fn parquet_sink_write_with_extension() -> Result<()> {
+        let filename = "test_file.custom_ext";
+        let file_path = format!("file:///path/to/{}", filename);
+        let parquet_sink = create_written_parquet_sink(file_path.as_str()).await?;
+
+        // assert written
+        let mut written = parquet_sink.written();
+        let written = written.drain();
+        assert_eq!(
+            written.len(),
+            1,
+            "expected a single parquet file to be written, instead found {}",
+            written.len()
+        );
+
+        let (path, ..) = written.take(1).next().unwrap();
+
+        let path_parts = path.parts().collect::<Vec<_>>();
+        assert_eq!(
+            path_parts.len(),
+            3,
+            "Expected 3 path parts, instead found {}",
+            path_parts.len()
+        );
+        assert_eq!(path_parts.last().unwrap().as_ref(), filename);
+
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn parquet_sink_write_with_directory_name() -> Result<()> {
+        let file_path = "file:///path/to";
+        let parquet_sink = create_written_parquet_sink(file_path).await?;
+
+        // assert written
+        let mut written = parquet_sink.written();
+        let written = written.drain();
+        assert_eq!(
+            written.len(),
+            1,
+            "expected a single parquet file to be written, instead found {}",
+            written.len()
+        );
+
+        let (path, ..) = written.take(1).next().unwrap();
+
+        let path_parts = path.parts().collect::<Vec<_>>();
+        assert_eq!(
+            path_parts.len(),
+            3,
+            "Expected 3 path parts, instead found {}",
+            path_parts.len()
+        );
+        assert!(path_parts.last().unwrap().as_ref().ends_with(".parquet"));
+
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn parquet_sink_write_with_folder_ending() -> Result<()> {
+        let file_path = "file:///path/to/";
+        let parquet_sink = create_written_parquet_sink(file_path).await?;
+
+        // assert written
+        let mut written = parquet_sink.written();
+        let written = written.drain();
+        assert_eq!(
+            written.len(),
+            1,
+            "expected a single parquet file to be written, instead found {}",
+            written.len()
+        );
+
+        let (path, ..) = written.take(1).next().unwrap();
+
+        let path_parts = path.parts().collect::<Vec<_>>();
+        assert_eq!(
+            path_parts.len(),
+            3,
+            "Expected 3 path parts, instead found {}",
+            path_parts.len()
+        );
+        assert!(path_parts.last().unwrap().as_ref().ends_with(".parquet"));
+
+        Ok(())
+    }
+
+    async fn create_written_parquet_sink(table_path: &str) -> Result<Arc<ParquetSink>> {
+        let field_a = Field::new("a", DataType::Utf8, false);
+        let field_b = Field::new("b", DataType::Utf8, false);
+        let schema = Arc::new(Schema::new(vec![field_a, field_b]));
+        let object_store_url = ObjectStoreUrl::local_filesystem();
+
+        let file_sink_config = FileSinkConfig {
+            object_store_url: object_store_url.clone(),
+            file_groups: vec![PartitionedFile::new("/tmp".to_string(), 1)],
+            table_paths: vec![ListingTableUrl::parse(table_path)?],
+            output_schema: schema.clone(),
+            table_partition_cols: vec![],
+            insert_op: InsertOp::Overwrite,
+            keep_partition_by_columns: false,
+        };
+        let parquet_sink = Arc::new(ParquetSink::new(
+            file_sink_config,
+            TableParquetOptions {
+                key_value_metadata: std::collections::HashMap::from([
+                    ("my-data".to_string(), Some("stuff".to_string())),
+                    ("my-data-bool-key".to_string(), None),
+                ]),
+                ..Default::default()
+            },
+        ));
+
+        // create data
+        let col_a: ArrayRef = Arc::new(StringArray::from(vec!["foo", "bar"]));
+        let col_b: ArrayRef = Arc::new(StringArray::from(vec!["baz", "baz"]));
+        let batch = RecordBatch::try_from_iter(vec![("a", col_a), ("b", col_b)]).unwrap();
+
+        // write stream
+        parquet_sink
+            .write_all(
+                Box::pin(RecordBatchStreamAdapter::new(
+                    schema,
+                    futures::stream::iter(vec![Ok(batch)]),
+                )),
+                &build_ctx(object_store_url.as_ref()),
+            )
+            .await
+            .unwrap();
+
+        Ok(parquet_sink)
+    }
+
     #[tokio::test]
     async fn parquet_sink_write_partitions() -> Result<()> {
         let field_a = Field::new("a", DataType::Utf8, false);

datafusion/core/src/datasource/file_format/write/demux.rs

@@ -59,8 +59,9 @@ type DemuxedStreamReceiver = UnboundedReceiver<(Path, RecordBatchReceiver)>;
 /// which should be contained within the same output file. The outer channel
 /// is used to send a dynamic number of inner channels, representing a dynamic
 /// number of total output files. The caller is also responsible to monitor
-/// the demux task for errors and abort accordingly. The single_file_output parameter
-/// overrides all other settings to force only a single file to be written.
+/// the demux task for errors and abort accordingly. A path with an extension will
+/// force only a single file to be written with the extension from the path. Otherwise
+/// the default extension will be used and the output will be split into multiple files.
 /// partition_by parameter will additionally split the input based on the unique
 /// values of a specific column `<https://github.com/apache/datafusion/issues/7744>``
 ///                                                                              ┌───────────┐               ┌────────────┐    ┌─────────────┐
@@ -79,12 +80,13 @@ pub(crate) fn start_demuxer_task(
     context: &Arc<TaskContext>,
     partition_by: Option<Vec<(String, DataType)>>,
     base_output_path: ListingTableUrl,
-    file_extension: String,
+    default_extension: String,
     keep_partition_by_columns: bool,
 ) -> (SpawnedTask<Result<()>>, DemuxedStreamReceiver) {
     let (tx, rx) = mpsc::unbounded_channel();
     let context = context.clone();
-    let single_file_output = !base_output_path.is_collection();
+    let single_file_output =
+        !base_output_path.is_collection() && base_output_path.file_extension().is_some();
     let task = match partition_by {
         Some(parts) => {
             // There could be an arbitrarily large number of parallel hive style partitions being written to, so we cannot
@@ -96,7 +98,7 @@ pub(crate) fn start_demuxer_task(
                     context,
                     parts,
                     base_output_path,
-                    file_extension,
+                    default_extension,
                     keep_partition_by_columns,
                 )
                 .await
@@ -108,7 +110,7 @@ pub(crate) fn start_demuxer_task(
                 input,
                 context,
                 base_output_path,
-                file_extension,
+                default_extension,
                 single_file_output,
             )
             .await

datafusion/core/src/datasource/listing/url.rs

@@ -190,6 +190,19 @@ impl ListingTableUrl {
         self.url.path().ends_with(DELIMITER)
     }
 
+    /// Returns the file extension of the last path segment if it exists
+    pub fn file_extension(&self) -> Option<&str> {
+        if let Some(segments) = self.url.path_segments() {
+            if let Some(last_segment) = segments.last() {
+                if last_segment.contains(".") && !last_segment.ends_with(".") {
+                    return last_segment.split('.').last();
+                }
+            }
+        }
+
+        None
+    }
+
     /// Strips the prefix of this [`ListingTableUrl`] from the provided path, returning
     /// an iterator of the remaining path segments
     pub(crate) fn strip_prefix<'a, 'b: 'a>(
@@ -493,4 +506,54 @@ mod tests {
             "path not ends with / - fragment ends with / - not collection",
         );
     }
+
+    #[test]
+    fn test_file_extension() {
+        fn test(input: &str, expected: Option<&str>, message: &str) {
+            let url = ListingTableUrl::parse(input).unwrap();
+            assert_eq!(url.file_extension(), expected, "{message}");
+        }
+
+        test("https://a.b.c/path/", None, "path ends with / - not a file");
+        test(
+            "https://a.b.c/path/?a=b",
+            None,
+            "path ends with / - with query args - not a file",
+        );
+        test(
+            "https://a.b.c/path?a=b/",
+            None,
+            "path not ends with / - query ends with / but no file extension",
+        );
+        test(
+            "https://a.b.c/path/#a=b",
+            None,
+            "path ends with / - with fragment - not a file",
+        );
+        test(
+            "https://a.b.c/path#a=b/",
+            None,
+            "path not ends with / - fragment ends with / but no file extension",
+        );
+        test(
+            "file///some/path/",
+            None,
+            "file path ends with / - not a file",
+        );
+        test(
+            "file///some/path/file",
+            None,
+            "file path does not end with - no extension",
+        );
+        test(
+            "file///some/path/file.",
+            None,
+            "file path ends with . - no value after .",
+        );
+        test(
+            "file///some/path/file.ext",
+            Some("ext"),
+            "file path ends with .ext - extension is ext",
+        );
+    }
 }