arnabnandy7 opened a new pull request, #23166:
URL: https://github.com/apache/kafka/pull/23166

   A non-materialized `KTable#transformValues()` recomputes values from its 
parent when a downstream operation performs a table lookup. This can produce an 
incorrect result when the transformer uses a connected state store whose 
contents have changed since the original record was processed.
   
   This change internally materializes the result of `transformValues()` when 
state-store names are supplied. Downstream lookups therefore return the value 
computed when the input record was processed instead of invoking the stateful 
transformer again.
   
   The `KTable` documentation now describes this behavior and clarifies that 
transformations relying only on transformer-local state still need to be 
explicitly materialized before downstream table lookups.
   
   Testing adds coverage for both DSL store formats. The regression test uses a 
store-backed counter transformer followed by a downstream join and verifies 
that the join reads the originally transformed value rather than recomputing it 
against the updated state.


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