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https://issues.apache.org/jira/browse/DRILL-7096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16914154#comment-16914154
 ] 

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

arina-ielchiieva commented on pull request #1829: DRILL-7096: Develop vector 
for canonical Map<K,V>
URL: https://github.com/apache/drill/pull/1829#discussion_r317073646
 
 

 ##########
 File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetReaderUtility.java
 ##########
 @@ -713,4 +715,63 @@ public static boolean 
containsComplexColumn(ParquetMetadata footer, List<SchemaP
     }
     return false;
   }
+
+  /**
+   * Converts list of {@link OriginalType}s to list of {@link 
org.apache.drill.common.types.TypeProtos.MajorType}s.
+   * <b>NOTE</b>: current implementation cares about {@link OriginalType#MAP} 
only
+   * converting it to {@link 
org.apache.drill.common.types.TypeProtos.MinorType#DICT}.
+   * Other original types are converted to {@code null}.
+   *
+   * @param originalTypes list of Parquet's types
+   * @return list containing either {@code null} or type with minor
+   *         type {@link 
org.apache.drill.common.types.TypeProtos.MinorType#DICT} values
+   */
+  public static List<TypeProtos.MajorType> getComplexTypes(List<OriginalType> 
originalTypes) {
+    List<TypeProtos.MajorType> result = new ArrayList<>();
+    if (originalTypes == null) {
+      return result;
+    }
+    for (OriginalType type : originalTypes) {
+      if (type == OriginalType.MAP) {
+        TypeProtos.MajorType drillType = TypeProtos.MajorType.newBuilder()
+            .setMinorType(TypeProtos.MinorType.DICT)
+            .setMode(TypeProtos.DataMode.OPTIONAL)
+            .build();
+        result.add(drillType);
+      } else {
+        result.add(null);
+      }
+    }
+
+    return result;
+  }
+
+  /**
+   * Checks whether group field matches pattern for Logical Map type:
+   *
+   * <map-repetition> group <name> (MAP) {
 
 Review comment:
   Use proper html formatting.
 
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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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