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https://issues.apache.org/jira/browse/DRILL-7096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16920807#comment-16920807
]
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_r319898307
##########
File path:
logical/src/main/java/org/apache/drill/common/expression/SchemaPath.java
##########
@@ -74,6 +74,26 @@ public static SchemaPath getCompoundPath(String... strings)
{
return new SchemaPath(s);
}
+ /**
+ * Constructs {@code SchemaPath} based on given {@code path} array up to
{@literal n}th element (inclusively).
+ *
+ * Example: for case when {@code n = 2} and {@code path = {"a", "b", "c",
"d", "e", ...}}
+ * the method returns {@code a.b}
+ *
+ * @param n number of elements in {@literal path} array to take when
constructing {@code SchemaPath}
+ * @param path column path used to construct schema path
+ * @return schema path containing {@literal n - 1} children
+ */
+ public static SchemaPath getCompoundPath(int n, String... path) {
Review comment:
This is cool that you added more flexible method, now method above with
signature ```public static SchemaPath getCompoundPath(String... strings)``` may
be rewritten to :
```java
public static SchemaPath getCompoundPath(String... strings) {
return getCompoundPath(strings.length, strings);
}
```
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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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