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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
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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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