Github user sirpkt commented on a diff in the pull request:
https://github.com/apache/tajo/pull/454#discussion_r28210054
--- Diff:
tajo-algebra/src/main/java/org/apache/tajo/algebra/WindowSpec.java ---
@@ -128,12 +128,14 @@ public boolean equals(Object obj) {
public static enum WindowFrameStartBoundType {
UNBOUNDED_PRECEDING,
CURRENT_ROW,
- PRECEDING
+ PRECEDING,
+ FOLLOWING
}
--- End diff --
I don't think only one rule is enough because start bound type and end
bound type can be the same.
For example, we can use ```rows between current row and current row``` as
followings
```
mydb=# select id, max(value) over (partition by id rows between current row
and current row) from test3;
id | max
----+-----
1 | 1
1 | 2
2 | 5
2 | 6
2 | 7
(5 rows)
```
So, actually there are two rules.
1) end bound cannot precede the start bound, but can be the same as the
start bound
2) UNBOUNDED PRECEDING cannot be an end bound and UNBOUNDED FOLLOWING
cannot be a start bound
However, I totally agree with you that the code becomes much simpler if we
use the unified bound type. So, I'll try to unify the bound type.
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