[GitHub] [druid] gianm commented on a change in pull request #10318: Fix handling of 'join' on top of 'union' datasources.

[GitBox <gi...@apache.org>]

gianm commented on a change in pull request #10318:
URL: https://github.com/apache/druid/pull/10318#discussion_r477443081



##########
File path: processing/src/main/java/org/apache/druid/query/UnionQueryRunner.java
##########
@@ -41,30 +42,27 @@ public UnionQueryRunner(
   public Sequence<T> run(final QueryPlus<T> queryPlus, final ResponseContext responseContext)
   {
     Query<T> query = queryPlus.getQuery();
-    DataSource dataSource = query.getDataSource();
-    if (dataSource instanceof UnionDataSource) {
+
+    final DataSourceAnalysis analysis = DataSourceAnalysis.forDataSource(query.getDataSource());
+
+    if (analysis.isConcreteTableBased() && analysis.getBaseTableDataSources().get().size() != 1) {

Review comment:
       Hmm, I was trying to avoid using `instanceof` checks outside of the DataSourceAnalysis class, and instead stick to cleanly defined interfaces as much as possible. So, I designed dataSourceAnalysis.getBaseTableDataSources() to encapsulate this logic (it has the `instanceof` check you're talking about).
   
   Do you think it'd be better to instead move the logic to UnionQueryRunner?




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