[
https://issues.apache.org/jira/browse/TAJO-1359?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14532855#comment-14532855
]
ASF GitHub Bot commented on TAJO-1359:
--------------------------------------
Github user jihoonson commented on a diff in the pull request:
https://github.com/apache/tajo/pull/422#discussion_r29862941
--- Diff:
tajo-plan/src/main/java/org/apache/tajo/plan/nameresolver/NameResolver.java ---
@@ -31,14 +34,30 @@
import org.apache.tajo.plan.verifier.VerifyException;
import org.apache.tajo.plan.logical.RelationNode;
import org.apache.tajo.util.Pair;
+import org.apache.tajo.util.StringUtils;
import org.apache.tajo.util.TUtil;
-import java.util.ArrayList;
+import java.util.Collection;
import java.util.List;
import java.util.Map;
+import java.util.Set;
/**
- * NameResolver utility
+ * Column name resolution utility. A SQL statement can include many kinds
of column names,
+ * defined in different ways. Some column name indicates just a column in
a relation.
+ * Another column name includes alias table name or alias column name,
derived from some expression.
+ *
+ * This utility ensures that each column name is derived from valid and
accessible column, and
+ * it also finds the exact data type of the column.
+ *
+ * Terminology:
+ * <ul>
+ * <li>Qualifier: database name, table name, or both included in a
column name</li>
+ * <li>Simple name: just column name without any qualifier</li>
--- End diff --
I have a question. When a column ```C``` has an alias ```A```, is its
simple name ```C``` or ```A```?
> Add nested field projector and language extension to project nested record
> --------------------------------------------------------------------------
>
> Key: TAJO-1359
> URL: https://issues.apache.org/jira/browse/TAJO-1359
> Project: Tajo
> Issue Type: Sub-task
> Components: parser, physical operator, planner/optimizer
> Reporter: Hyunsik Choi
> Assignee: Hyunsik Choi
> Fix For: 0.11.0
>
> Attachments: TAJO-1359.patch, TAJO-1359_2.patch, TAJO-1359_3.patch,
> TAJO-1359_4.patch, TAJO-1359_5.patch, TAJO-1359_6.patch, TAJO-1359_7.patch
>
>
> We need to improve Projector class to get nested record fields, and we also
> add some language extension to specify certain nested records in table
> schema. Both works should be done together. Otherwise, we need to test an
> entire work process.
> Using dot '.' would be good for the syntax to specify nested fields. Many
> systems (Hive, Google BigQuery, and Drill) already use this syntax. Probably,
> many users are familiar with this form.
> For example, if *employee* is a root nested record field and it includes
> *age* and *name* fields, consisting two fields lastname and firstname, we can
> specify them individually as follows:
> {code}
> SELECT employee.age, employee.name.lastname, employee.name.firstname FROM ...
> {code}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
