[GitHub] [druid] abhishekagarwal87 commented on a change in pull request #10318: Fix handling of 'join' on top of 'union' datasources.

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

abhishekagarwal87 commented on a change in pull request #10318:
URL: https://github.com/apache/druid/pull/10318#discussion_r477104655



##########
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:
       can we use more explicit condition such as `analysis.getBaseDataSource() instanceof UnionDataSource` than this `analysis.getBaseTableDataSources().get().size() != 1`?  May be the assumption around number of tables will not be valid in future. 




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