[jira] [Commented] (DRILL-7096) Develop vector for canonical Map

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-7096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16898963#comment-16898963 ] 

ASF GitHub Bot commented on DRILL-7096:
---------------------------------------

KazydubB commented on pull request #1829: DRILL-7096: Develop vector for canonical Map<K,V>
URL: https://github.com/apache/drill/pull/1829#discussion_r310163995
 
 

 ##########
 File path: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet2/DrillParquetReader.java
 ##########
 @@ -175,6 +183,38 @@ private static MessageType getProjection(MessageType schema,
     return projection;
   }
 
+  /**
+   * Get type from the supplied {@code type} corresponding to given {@code segment}.
+   * @param type type to extract field corresponding to segment
+   * @param segment segment which type will be returned
+   * @return type corresponding to the {@code segment} or {@code null} if there is no field found in {@code type}.
+   */
+  private static Type getType(Type type, PathSegment segment) {
+    Type result = null;
+    if (type != null && !type.isPrimitive()) {
+      GroupType groupType = type.asGroupType();
+      if (segment.isNamed()) {
+        boolean found = false;
+        String fieldName = segment.getNameSegment().getPath();
+        for (Type field : groupType.getFields()) {
+          if (field.getName().equalsIgnoreCase(fieldName)) {
+            fieldName = field.getName();
+            found = true;
+            break;
+          }
+        }
+        result = found ? groupType.getType(fieldName) : null;
+      } else {
+        // the segment is array index
+        if (groupType.getOriginalType() == OriginalType.LIST) {
+          // get element type of the list
+          result = groupType.getType(0).asGroupType().getType(0);
+        }
+      }
+    }
+    return result;
 
 Review comment:
   yes, it is OK.
 
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> Develop vector for canonical Map<K,V>
> -------------------------------------
>
>                 Key: DRILL-7096
>                 URL: https://issues.apache.org/jira/browse/DRILL-7096
>             Project: Apache Drill
>          Issue Type: Sub-task
>            Reporter: Igor Guzenko
>            Assignee: Bohdan Kazydub
>            Priority: Major
>             Fix For: 1.17.0
>
>
> Canonical Map<K,V> datatype can be represented using combination of three value vectors:
> keysVector - vector for storing keys of each map
> valuesVector - vector for storing values of each map
> offsetsVector - vector for storing of start indexes of next each map
> So it's not very hard to create such Map vector, but there is a major issue with such map representation. It's hard to search maps values by key in such vector, need to investigate some advanced techniques to make such search efficient. Or find other more suitable options to represent map datatype in world of vectors.
> After question about maps, Apache Arrow developers responded that for Java they don't have real Map vector, for now they just have logical Map type definition where they define Map like: List< Struct<key:key_type, value:value_type> >. So implementation of value vector would be useful for Arrow too.



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