[GitHub] okalinin commented on a change in pull request #1370: DRILL-5797: Use Parquet new reader more often

[GitBox <gi...@apache.org>]

okalinin commented on a change in pull request #1370: DRILL-5797: Use Parquet new reader more often
URL: https://github.com/apache/drill/pull/1370#discussion_r201344111
 
 

 ##########
 File path: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetReaderUtility.java
 ##########
 @@ -140,15 +140,87 @@ public static int getIntFromLEBytes(byte[] input, int start) {
     return out;
   }
 
+  /**
+   * Map full schema paths in format `a`.`b`.`c` to respective SchemaElement objects.
+   *
+   * @param footer Parquet file metadata
+   * @return       schema full path to SchemaElement map
+   */
   public static Map<String, SchemaElement> getColNameToSchemaElementMapping(ParquetMetadata footer) {
-    HashMap<String, SchemaElement> schemaElements = new HashMap<>();
+    Map<String, SchemaElement> schemaElements = new HashMap<>();
     FileMetaData fileMetaData = new ParquetMetadataConverter().toParquetMetadata(ParquetFileWriter.CURRENT_VERSION, footer);
-    for (SchemaElement se : fileMetaData.getSchema()) {
-      schemaElements.put(se.getName(), se);
+
+    Iterator iter = fileMetaData.getSchema().iterator();
+
+    // skip first default 'root' element
+    if (iter.hasNext()) {
 
 Review comment:
   First element in `FileMetaData.getSchema()` is default element named `root`. If we don't skip it, map keys would have format:
   `root`.`a`
   `root`.`b`
   etc.
   Correspondingly, comparison with `SchemaPath.toString()` representation would need to be implemented with that in mind (`root` part would have to be cut anyway). If this is considered to be better approach, I could implement it that way indeed.

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