Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/376#discussion_r53056521
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetGroupScan.java
---
@@ -529,6 +549,36 @@ public long getRowCount() {
}
+
+ // Create and return a new file selection based on reading the metadata
cache file.
+ // This function also initializes a few of ParquetGroupScan's fields as
appropriate.
+ private FileSelection
+ initFromMetadataCache(DrillFileSystem fs, FileSelection selection)
throws IOException {
+ FileStatus metaRootDir = selection.getFirstPath(fs);
+ Path metaFilePath = new Path(metaRootDir.getPath(),
Metadata.METADATA_FILENAME);
+
+ // get (and set internal field) the metadata for the directory by
reading the metadata file
+ this.parquetTableMetadata = Metadata.readBlockMeta(fs,
metaFilePath.toString());
+ List<String> fileNames = Lists.newArrayList();
+ for (Metadata.ParquetFileMetadata file :
parquetTableMetadata.getFiles()) {
+ fileNames.add(file.getPath());
+ }
+ // when creating the file selection, set the selection root in the
form /a/b instead of
+ // 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.
+ final Path metaRootPath =
Path.getPathWithoutSchemeAndAuthority(metaRootDir.getPath());
+ this.selectionRoot = metaRootPath.toString();
+
+ // Use the FileSelection constructor directly here instead of the
FileSelection.create() method
+ // because create() changes the root to include the scheme and
authority; In future, if create()
+ // is the preferred way to instantiate a file selection, we may need
to do something different...
+ FileSelection newSelection = new
FileSelection(selection.getStatuses(fs), fileNames, metaRootPath.toString());
--- End diff --
@jinfengni, as part of this PR I moved the expansion from
ParquetFormatPlugin to ParquetGroupScan for the metadata cache but did not
change the call to create FileSelection. I agree that the inconsistency could
be a problem. As @adeneche points out, DRILL-4380 has the background for the
change, but we really need to fix the FileSelection.create() interface, which
means we should prioritize DRILL-4381.
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