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https://issues.apache.org/jira/browse/TAJO-838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14260371#comment-14260371
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ASF GitHub Bot commented on TAJO-838:
-------------------------------------
Github user hyunsik commented on a diff in the pull request:
https://github.com/apache/tajo/pull/231#discussion_r22325621
--- Diff:
tajo-catalog/tajo-catalog-common/src/main/java/org/apache/tajo/catalog/CatalogUtil.java
---
@@ -868,4 +865,43 @@ public static KeyValueSet
newPhysicalProperties(StoreType type) {
return options;
}
+
+ /**
+ * Make a unique name by concatenating column names.
+ * The concatenation is performed in sequence of columns' occurrence in
the relation schema.
+ *
+ * @param originalSchema original relation schema
+ * @param columnNames column names which will be unified
+ * @return unified name
+ */
+ public static String getUnifiedSimpleColumnName(Schema originalSchema,
String[] columnNames) {
--- End diff --
How about the case that some column name includes other column names? In
this case, it works correctly?
> Improve query planner to utilize index
> --------------------------------------
>
> Key: TAJO-838
> URL: https://issues.apache.org/jira/browse/TAJO-838
> Project: Tajo
> Issue Type: Sub-task
> Components: planner/optimizer
> Reporter: Jihoon Son
> Assignee: Jihoon Son
> Priority: Minor
>
> Index can improve the query performance when the selectivity of query is high.
> Thus, query planner should decide whether index is used or not for a given
> query.
> The selectivity can be guessed using statistics.
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