ableegoldman commented on a change in pull request #9186:
URL: https://github.com/apache/kafka/pull/9186#discussion_r485218625
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File path:
streams/src/main/java/org/apache/kafka/streams/kstream/internals/KStreamKTableJoinProcessor.java
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@@ -58,22 +58,23 @@ public void init(final ProcessorContext context) {
@Override
public void process(final K1 key, final V1 value) {
- // we do join iff keys are equal, thus, if key is null we cannot join
and just ignore the record
- // If {@code keyMapper} returns {@code null} it implies there is no
match,
+ // We allow null keys unless {@code keyMapper} returns {@code null}
and we ignore it as invalid.
Review comment:
Well, if `mappedKey` is null then there can't be a match in the global
table since we can't do a lookup with a null key. I think what @mjsax means
here (correct me if wrong) is just that we could phrase it a bit differently to
say something like
```
// If the mappedKey is null, we ignore it as invalid. This should never
happen for KTables since keyMapper
// just returns the key, but for GlobalKTables a non-null key can result in
a null mappedKey. Since there
// can't be a match for a null mappedKey, we drop it
```
...or something. Thoughts?
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