rubenada commented on a change in pull request #1614: [CALCITE-3546] Improve
EnumerableDefaults nested loop join
URL: https://github.com/apache/calcite/pull/1614#discussion_r352023673
##########
File path:
linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java
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@@ -1852,6 +1866,104 @@ private boolean innerHasNext() {
return Linq4j.asEnumerable(result);
}
+ /**
+ * Implementation of nested loop join that, unlike {@link
#nestedLoopJoinAsList}, does not
+ * require to build the complete result as a list before returning it.
Instead, it iterates
+ * through the outer enumerable and inner enumerable and returns the results
step by step.
+ * It does not support RIGHT / FULL join.
+ */
+ private static <TSource, TInner, TResult> Enumerable<TResult>
nestedLoopJoinOptimized(
+ final Enumerable<TSource> outer, final Enumerable<TInner> inner,
+ final Predicate2<TSource, TInner> predicate,
+ Function2<TSource, TInner, TResult> resultSelector,
+ final JoinType joinType) {
+ if (joinType == JoinType.RIGHT || joinType == JoinType.FULL) {
+ throw new IllegalArgumentException("JoinType " + joinType + " is
unsupported");
+ }
+
+ return new AbstractEnumerable<TResult>() {
+ public Enumerator<TResult> enumerator() {
+ return new Enumerator<TResult>() {
+ private Enumerator<TSource> outerEnumerator = outer.enumerator();
+ private Enumerator<TInner> innerEnumerator = null;
+ private boolean outerMatch = false; // whether the outerValue has
matched an innerValue
+ private TSource outerValue;
+ private TInner innerValue;
+ private int state = 0; // 0 moving outer, 1 moving inner
+
+ @Override public TResult current() {
+ return resultSelector.apply(outerValue, innerValue);
+ }
+
+ @Override public boolean moveNext() {
+ while (true) {
+ switch (state) {
+ case 0:
+ // move outer
+ if (!outerEnumerator.moveNext()) {
+ return false;
+ }
+ outerValue = outerEnumerator.current();
+ if (innerEnumerator != null) {
+ innerEnumerator.close();
+ }
+ innerEnumerator = inner.enumerator();
+ outerMatch = false;
+ state = 1;
+ continue;
+ case 1:
+ // move inner
+ if (innerEnumerator.moveNext()) {
+ innerValue = innerEnumerator.current();
+ if (predicate.apply(outerValue, innerValue)) {
+ outerMatch = true;
+ switch (joinType) {
+ case ANTI: // try next outer row
+ state = 0;
+ continue;
+ case SEMI: // return result, and try next outer row
+ state = 0;
+ // fall through
+ default: // INNER and LEFT just return result
Review comment:
Ok, it will make it clearer. Change committed.
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