junegunn commented on code in PR #8360:
URL: https://github.com/apache/hbase/pull/8360#discussion_r3426858110
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hbase-client/src/main/java/org/apache/hadoop/hbase/filter/FuzzyRowFilter.java:
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@@ -216,9 +216,14 @@ public ReturnCode filterCell(final Cell c) {
return ReturnCode.INCLUDE;
}
}
- // NOT FOUND -> seek next using hint
+ // NOT FOUND -> seek next using hint or skip the current row.
lastFoundIndex = -1;
filterRow = true;
+ // For reverse scans, a non-matching row can recreate itself as the next
hint. Since fuzzy
+ // matching is row-key based, skip the whole non-matching row instead of
seeking to it again.
+ if (isReversed() && tracker.updateTracker(c) &&
tracker.isNextRowSameAs(c)) {
+ return ReturnCode.NEXT_ROW;
+ }
return ReturnCode.SEEK_NEXT_USING_HINT;
Review Comment:
Hmm, I have mixed feelings about this. If the `isNextRowSameAs` condition
doesn't hold during a reverse scan, `updateTracker` will be called again in
`getNextCellHint`. AFAICT, this duplicate call doesn't affect the correctness.
Since `getNextCellHint` is only called when `filterCell` returns
`SEEK_NEXT_USING_HINT`, we could unconditionally call `updateTracker` here, and
avoid it in `getNextCellHint`, but then `getNextCellHint` will no longer be
self-contained and tightly coupled with a preceding call of `filterCell`, so
I'm not sure if that's the right direction.
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