mwkang commented on code in PR #6900:
URL: https://github.com/apache/hbase/pull/6900#discussion_r2051976496
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hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java:
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@@ -832,7 +845,7 @@ private void updateMetricsStore(boolean memstoreRead) {
* @return null is the top cell doesn't change. Otherwise, the NextState to
return
*/
private NextState needToReturn(List<? super ExtendedCell> outResult) {
- if (!outResult.isEmpty() && topChanged) {
+ if (topChanged) {
Review Comment:
You're right that at the `StoreScanner` level, the behavior doesn't seem
immediately problematic.
However, the issue becomes visible on the client side when multiple column
families are involved — the row ends up getting split.
This happens because the result from `row2` is included in the first next()
call, which is supposed to return only `row1`.
As a result, the client receives fragmented results for `row2`.
To help illustrate the issue, I’ve added a reproducible test case.
If you run
[TestTopChanged.testTopChanged](https://github.com/mwkang/hbase/blob/ad4a2558c46c1291f14b02c4fd1fa02603202c5d/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestTopChanged.java)
on the
[feature/bug-demo-HBASE-29254](https://github.com/mwkang/hbase/tree/feature/bug-demo-HBASE-29254)
branch, you can observe the behavior directly.
Here’s what you’ll see:
- **With the `!outResult.isEmpty()` condition in
[`needToReturn`](https://github.com/mwkang/hbase/blob/ad4a2558c46c1291f14b02c4fd1fa02603202c5d/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java#L865)
(current behavior):**
```
RESULT: rowkey = row2, cf = cf2
RESULT: rowkey = row2, cf = cf1
```
- **Without the `!outResult.isEmpty()` condition (modified behavior):**
```
RESULT: rowkey = row2, cf = cf1, cf2
```
It would be great if you could take a look — I know it's a bit of a hassle,
but your feedback would be really helpful.
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