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https://issues.apache.org/jira/browse/TAJO-1415?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14491500#comment-14491500
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ASF GitHub Bot commented on TAJO-1415:
--------------------------------------
Github user jihoonson commented on a diff in the pull request:
https://github.com/apache/tajo/pull/454#discussion_r28204015
--- Diff:
tajo-core/src/main/java/org/apache/tajo/engine/function/window/CurrentValue.java
---
@@ -24,41 +24,34 @@
import org.apache.tajo.plan.function.WindowAggFunc;
import org.apache.tajo.storage.Tuple;
-public abstract class FirstValue extends WindowAggFunc<Datum> {
+public abstract class CurrentValue extends WindowAggFunc<Datum> {
- public FirstValue(Column[] columns) {
+ public CurrentValue(Column[] columns) {
super(columns);
}
@Override
public FunctionContext newContext() {
- return new FirstValueContext();
+ return new CurrentValueContext();
}
@Override
public void eval(FunctionContext ctx, Tuple params) {
- FirstValueContext firstValueCtx = (FirstValueContext)ctx;
- if(firstValueCtx.isSet == false) {
- firstValueCtx.isSet = true;
+ CurrentValueContext currentValueCtx = (CurrentValueContext)ctx;
if (params.get(0).isNotNull()) {
--- End diff --
This line seems to check whether ```params.get(0)``` is the ```NullDatum```
or not. In addition to this, we should check ```params.get(0)``` is actually
```null``` or not.
> Window frame support
> --------------------
>
> Key: TAJO-1415
> URL: https://issues.apache.org/jira/browse/TAJO-1415
> Project: Tajo
> Issue Type: Sub-task
> Components: distributed query plan, parser, physical operator,
> planner/optimizer
> Reporter: Keuntae Park
> Assignee: Keuntae Park
> Fix For: window function
>
>
> We can define frame clause in window definition like
> {code}
> [ RANGE | ROWS ] frame_start
> [ RANGE | ROWS ] BETWEEN frame_start AND frame_end
> {code}
> , where frame_start and frame_end can be one of
> {code}
> UNBOUNDED PRECEDING
> value PRECEDING
> CURRENT ROW
> value FOLLOWING
> UNBOUNDED FOLLOWING
> {code}
> According to the window functions description of
> PostgreSQL(http://www.postgresql.org/docs/9.4/static/functions-window.html),
> there are two types of window functions based on window frame support.
> 1) row_number, rank, dense_rank, percent_rank, cume_dist, tile, lag and lead:
> these functions only work within window partition, which means window frame
> has no effect on these functions.
> 2) first_value, last_value, nth_value, and aggregation function as as window
> function: these functions should work with rows within window frame.
> Currently, Tajo parser recognize the window frame grammar but windowAggExec
> does not use that information.
> It works as if window frame is set as "RANGE BETWEEN UNBOUND PROCEEDING AND
> UNBOUNDED FOLLOWING", which is different from the default window frame
> setting of most DBMSs "RANGE BETWEEN UNBOUND PROCEEDING AND CURRENT ROW".
> Following should be done:
> 1) Applying correct default window frame for first_value, last_value,
> nth_value, and aggregation functions .
> 2) Supporting various window frame expressions.
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