Reasoning/Need:

Now that we're adding Range, a single field could be associated with multiple encrypted indices–in particular, both Range and Equality. So, when a field is being analyzed in an FLE2 supported queries context, that field could be associated with a set of queries. And, thus, every member of that query set should be checked (i.e., confirm that it's a currently supported type).

The critical change begins in resolved_encryption_info.h by changing:

stdx::variant<FleAlgorithmEnum, Fle2AlgorithmInt> algorithm;  

TO:
stdx::variant<FleAlgorithmEnum, std::set<Fle2AlgorithmInt>> algorithm;
 
(unless a better type has been determined). 
 

Details:

Main files:

resolved_encryption_info.cpp & resolved_encryption_info.h (src>mongo>db>modules>enterprise>src>fle>query_analysis)

Notes:

Examples of functions that will likely need to be modified (in resolved_encryption_info.cpp):

• ResolvedEncryptionInfo constructor. E.g.,:

• • initialize algorithm as something like std::set<Fle2AlgorithmInt> algorithm;
    • would then set to default kUnindexed IF the set is empty before type checking at the end of the constructor
  • instead of algorithm = Fle2AlgorithmInt::kRange, would use something like algorithm.insert(Fle2AlgorithmInt::kEquality)
• algorithmIs(Fle2AlgorithmInt fle2Alg)
  • instead of the current get_if<FleAlgorithmEnum>
  • do something like: ...get_if<std::set<Fle2AlgorithmInt>>...