mjsax commented on code in PR #20605:
URL: https://github.com/apache/kafka/pull/20605#discussion_r2388371695
##########
streams/src/main/java/org/apache/kafka/streams/kstream/internals/foreignkeyjoin/SubscriptionSendProcessorSupplier.java:
##########
@@ -128,47 +128,105 @@ public void process(final Record<KLeft, Change<VLeft>>
record) {
}
private void leftJoinInstructions(final Record<KLeft, Change<VLeft>>
record) {
- if (record.value().oldValue != null) {
- final KRight oldForeignKey =
foreignKeyExtractor.extract(record.key(), record.value().oldValue);
- final KRight newForeignKey = record.value().newValue == null ?
null : foreignKeyExtractor.extract(record.key(), record.value().newValue);
- if (oldForeignKey != null &&
!Arrays.equals(serialize(newForeignKey), serialize(oldForeignKey))) {
+ final VLeft oldValue = record.value().oldValue;
+ final VLeft newValue = record.value().newValue;
+
+ if (oldValue == null && newValue == null) {
+ // no output for idempotent left hand side deletes
+ return;
+ }
+
+ final KRight oldForeignKey = oldValue == null ? null :
foreignKeyExtractor.extract(record.key(), oldValue);
+ final KRight newForeignKey = newValue == null ? null :
foreignKeyExtractor.extract(record.key(), newValue);
+
+ final boolean maybeUnsubscribe = oldForeignKey != null;
+ if (maybeUnsubscribe) {
+ // delete old subscription only if FK changed
+ //
+ // if FK did change, we need to explicitly delete the old
subscription,
+ // because the new subscription goes to a different partition
+ final boolean foreignKeyChanged =
!Arrays.equals(serialize(newForeignKey), serialize(oldForeignKey));
+
+ if (foreignKeyChanged) {
+ // this may lead to unnecessary tombstones if the old FK
did not join;
+ // however, we cannot avoid it as we have no means to know
if the old FK joined or not
forward(record, oldForeignKey, DELETE_KEY_NO_PROPAGATE);
}
- forward(record, newForeignKey,
PROPAGATE_NULL_IF_NO_FK_VAL_AVAILABLE);
- } else if (record.value().newValue != null) {
- final KRight newForeignKey =
foreignKeyExtractor.extract(record.key(), record.value().newValue);
- forward(record, newForeignKey,
PROPAGATE_NULL_IF_NO_FK_VAL_AVAILABLE);
}
+
+ // for all cases (insert, update, and delete), we send a new
subscription;
+ // we need to get a response back for all cases to always produce
a left-join result
+ //
+ // note: for delete, `newForeignKey` is null, what is a "hack"
+ // no actual subscription will be added for null-FK on the right
hand sice, but we still get the response back we need
+ //
+ // this may lead to unnecessary tombstones if the old FK did not
join;
+ // however, we cannot avoid it as we have no means to know if the
old FK joined or not
+ forward(record, newForeignKey,
PROPAGATE_NULL_IF_NO_FK_VAL_AVAILABLE);
}
private void defaultJoinInstructions(final Record<KLeft,
Change<VLeft>> record) {
- if (record.value().oldValue != null) {
- final KRight oldForeignKey =
foreignKeyExtractor.extract(record.key(), record.value().oldValue);
- final KRight newForeignKey = record.value().newValue == null ?
null : foreignKeyExtractor.extract(record.key(), record.value().newValue);
+ final VLeft oldValue = record.value().oldValue;
+ final VLeft newValue = record.value().newValue;
+
+ final KRight oldForeignKey = oldValue == null ? null :
foreignKeyExtractor.extract(record.key(), oldValue);
+ final boolean needToUnsubscribe = oldForeignKey != null;
- if (oldForeignKey == null && newForeignKey == null) {
+ // if left row is inserted or updated, subscribe to new FK (if new
FK is valid)
+ if (newValue != null) {
+ final KRight newForeignKey =
foreignKeyExtractor.extract(record.key(), newValue);
+
+ if (newForeignKey == null) { // invalid FK
logSkippedRecordDueToNullForeignKey();
- } else if (oldForeignKey == null) {
- forward(record, newForeignKey,
PROPAGATE_ONLY_IF_FK_VAL_AVAILABLE);
- } else if (newForeignKey == null) {
- forward(record, oldForeignKey, DELETE_KEY_AND_PROPAGATE);
- } else if (!Arrays.equals(serialize(newForeignKey),
serialize(oldForeignKey))) {
- //Different Foreign Key - delete the old key value and
propagate the new one.
- //Delete it from the oldKey's state store
- forward(record, oldForeignKey, DELETE_KEY_NO_PROPAGATE);
- //Add to the newKey's state store. Additionally, propagate
null if no FK is found there,
- //since we must "unset" any output set by the previous
FK-join. This is true for both INNER
- //and LEFT join.
- forward(record, newForeignKey,
PROPAGATE_NULL_IF_NO_FK_VAL_AVAILABLE);
- } else { // unchanged FK
- forward(record, newForeignKey,
PROPAGATE_ONLY_IF_FK_VAL_AVAILABLE);
+ if (needToUnsubscribe) {
+ // delete old subscription
+ //
+ // this may lead to unnecessary tombstones if the old
FK did not join;
+ // however, we cannot avoid it as we have no means to
know if the old FK joined or not
+ forward(record, oldForeignKey,
DELETE_KEY_AND_PROPAGATE);
+ }
+ } else { // valid FK
Review Comment:
Not sure if I can follow?
```
if (newForeignKey = null) {
...
} else { // what would we add here? -> `else if (newForeignKey != null)`
would be redundant
...
}
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