utafrali commented on code in PR #29646:
URL: https://github.com/apache/flink/pull/29646#discussion_r4397499952
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flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/operators/join/interval/TimeIntervalJoin.java:
##########
@@ -321,8 +321,10 @@ public void processElement1(RowData leftRow, Context ctx,
Collector<RowData> out
// ordered keys.
}
}
- // Check if we need to cache the current row.
- if (rightOperatorTime < rightQualifiedUpperBound) {
+ // Check if we need to cache the current row. A row that can never
match is only cached to
+ // pad it with nulls once its window has closed.
+ if (rightOperatorTime < rightQualifiedUpperBound
+ && (joinType.isLeftOuter() ||
!joinFunction.currentKeyCannotMatch())) {
Review Comment:
The guard `joinType.isLeftOuter() || !joinFunction.currentKeyCannotMatch()`
evaluates `currentKeyCannotMatch()` on every record on the hot per-record path,
re-running the null-check even for records that are kept. Since the result only
depends on the current join key, consider caching it once per key change, or at
minimum short-circuiting via the cheaper `!nullSafe` check first. Minor perf
concern given the "runtime per-record code paths" sensitivity flagged in the PR
template.
##########
flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/operators/join/interval/IntervalJoinFunction.java:
##########
@@ -90,4 +87,12 @@ public TypeInformation<RowData> getProducedType() {
public void setJoinKey(RowData currentKey) {
this.joinKey = (NullAwareGetters) currentKey;
}
+
+ /**
+ * Returns whether no record of the current join key can ever match,
because the key has a null
+ * in a field that is not null-safe. The join key must be set.
+ */
+ public boolean currentKeyCannotMatch() {
Review Comment:
The javadoc states "The join key must be set" but there is no guard
(assertion or null check) to catch misuse. Since `currentKeyCannotMatch()` is
now a public method exposed to callers like `TimeIntervalJoin`, consider adding
`Preconditions.checkState(joinKey != null, "joinKey must be set via
setJoinKey() before calling currentKeyCannotMatch()")` to make the contract
explicit and fail fast if the ordering is ever violated.
##########
flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/operators/join/window/utils/WindowJoinHelper.java:
##########
@@ -98,6 +103,8 @@ public WindowJoinHelper(
this.collector = collector;
this.windowJoinProcessor = getWindowJoinProcessor(joinType);
+ this.leftUnmatchedIsEmitted = joinType.isLeftOuter() || joinType ==
FlinkJoinType.ANTI;
+ this.rightUnmatchedIsEmitted = joinType.isRightOuter();
Review Comment:
The derivation `leftUnmatchedIsEmitted = joinType.isLeftOuter() || joinType
== FlinkJoinType.ANTI` mixes a method call with a direct enum comparison. For
readability and parity with `rightUnmatchedIsEmitted`, consider either
introducing a helper (e.g. `joinType.emitsUnmatchedLeft()`) on `FlinkJoinType`,
or at minimum adding a brief inline comment explaining why SEMI is excluded but
ANTI is included (SEMI drops unmatched left rows while ANTI emits them). Future
readers will otherwise need to re-derive this from the join semantics.
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