[GitHub] [kafka] ableegoldman commented on a change in pull request #9582: KAFKA-6687: rewrite topology to allow creating multiple KStreams from the same topic

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ableegoldman commented on a change in pull request #9582:
URL: https://github.com/apache/kafka/pull/9582#discussion_r520959288



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File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/InternalTopologyBuilder.java
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@@ -410,18 +410,6 @@ public final void addSource(final Topology.AutoOffsetReset offsetReset,
             }
         }
 
-        for (final Pattern otherPattern : earliestResetPatterns) {
-            if (topicPattern.pattern().contains(otherPattern.pattern()) || otherPattern.pattern().contains(topicPattern.pattern())) {
-                throw new TopologyException("Pattern " + topicPattern + " will overlap with another pattern " + otherPattern + " already been registered by another source");
-            }
-        }
-
-        for (final Pattern otherPattern : latestResetPatterns) {
-            if (topicPattern.pattern().contains(otherPattern.pattern()) || otherPattern.pattern().contains(topicPattern.pattern())) {
-                throw new TopologyException("Pattern " + topicPattern + " will overlap with another pattern " + otherPattern + " already been registered by another source");
-            }
-        }
-

Review comment:
       Saw this and at first I thought it was broken because it only considers pattern-subscribed topics that happened to explicitly configure an offset reset policy. Unless I'm missing something here, that makes no sense and we should consider _all_  source patterns and whether they overlap.
   But then I started thinking, why does it matter if they overlap? Just because one pattern is a substring of another does not mean that they'll match the same topics. So I think that we should actually just remove this restriction altogether. Am I missing anything here?




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