Rule Definition
Calculated fields result from functions like string functions (CONCAT, RTRIM, ...)and CASE expressions. Note that all fields provided by a table function act as calculated. For a calculated field to be used (as a filter or join condition) the values of this field for every row must be evaluated at this point of processing. That may be very time-consuming

Remediation
Evaluate results in your code after accessing CDS views when this is possible.

Violation Code Sample

define view TEST_VIEW1 as
       select from
       TEST_VIEW2
        inner join
            /amr/ui_inputs  as inputs
        on
            rat_rule_t.spras  = LTRIM( inputs.i_language, ' ' )
----------------------------------------
define view TEST_VIEW1 as
       select from
       TEST_VIEW2
    WHERE 
        rat_rule_t.spras  = CASE rat_rule_t.spras WHEN 1 THEN 'a' ELSE 'b' END

https://www.sap.com/documents/2019/01/0e6d5904-367d-0010-87a3-c30de2ffd8ff.html