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https://issues.apache.org/jira/browse/TAJO-838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14243861#comment-14243861
]
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_r21732356
--- Diff: tajo-plan/src/main/java/org/apache/tajo/plan/LogicalPlan.java ---
@@ -147,20 +149,33 @@ public String generateUniqueColumnName(EvalNode
evalNode) {
return attachSeqIdToGeneratedColumnName(prefix).toLowerCase();
}
+ public String generateUniqueColumnName(Expr expr) {
+ return generateUniqueColumnName(expr, false);
+ }
+
/**
* It generates an unique column name from Expr. It is usually used for
an expression or predicate without
* a specified name (i.e., alias).
+ * Here, some expressions require to be identified with their names in
the future.
+ * For example, expressions must be identifiable with their names when
getting targets in {@link LogicalPlanner#visitCreateIndex}.
*/
- public String generateUniqueColumnName(Expr expr) {
+ public String generateUniqueColumnName(Expr expr, boolean identifiable) {
String generatedName;
if (expr.getType() == OpType.Column) {
generatedName = ((ColumnReferenceExpr) expr).getCanonicalName();
+ } else if (identifiable) {
+ generatedName = generateUniqueIdentifiableColumnName(expr);
} else { // if a generated column name
generatedName =
attachSeqIdToGeneratedColumnName(getGeneratedPrefixFromExpr(expr));
}
return generatedName;
}
+ private String generateUniqueIdentifiableColumnName(Expr expr) {
+ IdentifiableNameBuilder nameBuilder = new
IdentifiableNameBuilder(expr);
--- End diff --
Its purpose looks similar to the original generateUniqueColumnName. You may
make it due to some bugs of generateUniqueColumnName. I think that it would
better if you fix some bug of generateUniqueColumnName instead of making new
implementation.
> 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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