[GitHub] [druid] gianm commented on issue #9412: Regression: SQL query with multiple similar CASE clauses cannot be translated to correct native json format

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

gianm commented on issue #9412: Regression: SQL query with multiple similar CASE clauses cannot be translated to correct native json format
URL: https://github.com/apache/druid/issues/9412#issuecomment-591689543
 
 
   To be clear, the query @clintropolis is the correct way to write what you're trying to write. Starting in Druid 0.17.0 it (correctly) recognizes that `CASE cityName WHEN NULL THEN FALSE ELSE TRUE END AS col_a` is always true, because `NULL` does not equal `NULL`, so even if `cityName` is NULL, it still shouldn't go down the `WHEN NULL` path.
   
   PostgreSQL would do the same thing (I just tested it to double-check).
   
   There is a bug, though, where the SQL planner is trying to create two virtual columns with the same name. We'll need to fix that. But it shouldn't block you, @sascha-coenen, because you should adjust your query to the variant @clintropolis suggested anyway (it's better aligned with how SQL works, and should be effective in 0.17.0 and all future versions).

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