The following files contain string manipulation code used for execution of MQL expressions:

• https://github.com/mongodb/mongo/blob/0a68308f0d39a928ed551f285ba72ca560c38576/src/mongo/db/query/str_trim_utils.h
• https://github.com/mongodb/mongo/blob/0a68308f0d39a928ed551f285ba72ca560c38576/src/mongo/db/query/substr_utils.h

They are used both by the expression evaluator in mongo::exec::expression namespace as well as by the SBE VM. The source code currently resides in the db/query directory. Although we are still in the process of improving the ownership and structure of db/query, code which is part of the classic or SBE execution engines should reside in the db/exec directory. This ticket proposes moving these files to db/exec.