GH-3207: ParquetFileReader supports detachFileInputStream (#3208)

Author: pan3793

parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java

@@ -729,7 +729,7 @@ public static ParquetFileReader open(InputFile file, ParquetReadOptions options,
     return new ParquetFileReader(file, options, f);
   }
 
-  protected final SeekableInputStream f;
+  protected SeekableInputStream f;
   private final InputFile file;
   private final ParquetReadOptions options;
   private final Map<ColumnPath, ColumnDescriptor> paths = new HashMap<>();
@@ -1741,6 +1741,14 @@ public OffsetIndex readOffsetIndex(ColumnChunkMetaData column) throws IOExceptio
         Util.readOffsetIndex(f, offsetIndexDecryptor, offsetIndexAAD));
   }
 
+  /**
+   * Explicitly detach the the input stream for the file to avoid being closed via
+   * {@link ParquetFileReader#close()}.
+   */
+  public void detachFileInputStream() {
+    f = null;
+  }
+
   @Override
   public void close() throws IOException {
     try {