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https://issues.apache.org/jira/browse/DRILL-7096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16895196#comment-16895196
 ] 

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

ihuzenko commented on pull request #1829: DRILL-7096: Develop vector for 
canonical Map<K,V>
URL: https://github.com/apache/drill/pull/1829#discussion_r308173710
 
 

 ##########
 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:
   is it ok that ```null``` returned here when ```type.isPrimitive()``` returns 
true ?  
 
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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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