smengcl commented on code in PR #9813:
URL: https://github.com/apache/ozone/pull/9813#discussion_r3533112410
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hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/RDBTable.java:
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@@ -99,16 +99,16 @@ public boolean isEmpty() throws RocksDatabaseException {
@Override
public boolean isExist(byte[] key) throws RocksDatabaseException {
rdbMetrics.incNumDBKeyMayExistChecks();
- final Supplier<byte[]> holder = db.keyMayExist(family, key);
- if (holder == null) {
- return false; // definitely not exists
- }
- final byte[] value = holder.get();
- if (value != null) {
- return true; // definitely exists
+ final Supplier<byte[]> valueSupplier = db.keyMayExist(family, key);
+ if (valueSupplier != null) {
+ final byte[] value = valueSupplier.get();
+ if (value != null) {
+ return true; // definitely exists
+ }
}
- // inconclusive: the key may or may not exist
+ // keyMayExist can be a false-negative in some RocksDB setups (for example,
+ // snapshot/checkpoint DBs). Verify via point-get to preserve correctness.
final boolean exists = get(key) != null;
Review Comment:
Sorry about the confusion. The comment has been reworded:
```
// keyMayExist could not return the value; confirm via point-get.
```
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