DRILL-2618: handle queries over empty folders consistently so that they report table not found rather than failing.

Refactor FileSelection to eliminate redundancy, make it more managable
Fix WorkspaceSchemaFactory to handle empty folders.
Introduce ParquetFileSelection, a sub-class of FileSelection that carries along metadata cache
Fix MagicStringMatcher so that it operate on files only.
Unit test file selection

1 files changed, 3 insertions, 3 deletions

diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetFormatPlugin.java b/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetFormatPlugin.java
index 91cd11255..4932aafb4 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetFormatPlugin.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetFormatPlugin.java
@@ -234,9 +234,9 @@ public class ParquetFormatPlugin implements FormatPlugin{
         // file:/a/b.  The reason is that the file names above have been created in the form
         // /a/b/c.parquet and the format of the selection root must match that of the file names
         // otherwise downstream operations such as partition pruning can break.
-        Path metaRootPath = Path.getPathWithoutSchemeAndAuthority(metaRootDir.getPath());
-        return new FileSelection(fileNames, metaRootPath.toString(), metadata, /* save metadata for future use */
-            selection.getFileStatusList(fs));
+        final Path metaRootPath = Path.getPathWithoutSchemeAndAuthority(metaRootDir.getPath());
+        final FileSelection newSelection = FileSelection.create(null, fileNames, metaRootPath.toString());
+        return ParquetFileSelection.create(newSelection, metadata);
       } else {
         // don't expand yet; ParquetGroupScan's metadata gathering operation
         // does that.