gustavodemorais commented on PR #26926:
URL: https://github.com/apache/flink/pull/26926#issuecomment-3347363254

   On another note, do you think it makes sense to remove the position 0 from 
all arrays related to joins? Right now, for N inputs, all arrays in the explain 
are of length N. However, for N inputs, we have N - 1 joins.
   
   The first position of all arrays in the MultiJoin node related to joins are 
a special case. Each position in the array is related to the join between 
inputs `i` and `i - 1`. The position `0` has some default values since these 
are the values related to joining input 0 and "input -1". For example, a 
regular two way join has arrays with a length of two for the properties
   ```
   joinTypes=[INNER, INNER],
   inputUniqueKeys=[(user_id), (order_id, user_id)] 
   joinConditions=[true, =(user_id, user_id0)]
   ```
   
   Calcite creates as a default value for pos 0. The same thing with the 
joinTypes, the first position is always INNER. In general, I think it either 
makes sense keep the position 0 like above for all attributes so they have the 
same length _or_ remove for it only for the join-related attributes. What do 
you think?


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