rubenada commented on a change in pull request #1101: [CALCITE-2909] Optimize
Enumerable SemiJoin with lazy computation of innerLookup (Ruben Quesada Lopez)
URL: https://github.com/apache/calcite/pull/1101#discussion_r268195878
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File path:
linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java
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@@ -1298,11 +1298,11 @@ private void closeInner() {
final EqualityComparer<TKey> comparer) {
return new AbstractEnumerable<TSource>() {
public Enumerator<TSource> enumerator() {
- final Enumerable<TKey> innerLookup =
- comparer == null
- ? inner.select(innerKeySelector).distinct()
- : inner.select(innerKeySelector).distinct(comparer);
-
+ // CALCITE-2909 Delay the computation of the innerLookup until the
moment when we are sure
+ // that it will be really needed, i.e. when the first outer enumerator
item is processed
+ final Enumerable<TKey> innerLookup = comparer == null
+ ? Linq4j.lazyEnumerable(() ->
inner.select(innerKeySelector).distinct())
+ : Linq4j.lazyEnumerable(() ->
inner.select(innerKeySelector).distinct(comparer));
Review comment:
No problem @asereda-gs , yours was an interesting approach too
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