C++: Remove some unused legacy relations from the DB scheme

[jketema]

Remove the following legacy relations:

• externalData
• snapshotDate
• duplicateCode
• similarCode
• tokens

This is similar to the following C# change #7746

[MathiasVP]

There are a couple of compile errors in CodeDuplication.qll now. For example:

ERROR: Could not resolve type @duplication_or_similarity (/home/runner/work/semmle-code/semmle-code/ql/cpp/ql/src/external/CodeDuplication.qll:14,20-46)

I think we should redefine the Copy class as:

private newtype TCopy = MkCopy() // Or whatever

/**
 * DEPRECATED: This class is no longer used.
 * 
 * A token block used for detection of duplicate and similar code.
 */
class Copy extends TCopy { ... }

and replace body of the predicates that refer to non-existing tables with none(). Hopefully, that means that existing code that uses these classes will still compile.

For CodeQL we have a 6 months deprecation notice. So 6 months from now we can finally delete this code for real!

How does that sound?

[jketema]

Sound like a plan.

[MathiasVP]

Almost LGTM! The QLDoc Check is complaining because we don't have QLDoc on:

• The external/CodeDuplication.qll file, and
• the CodeDuplication::SimilarBlock class.

I think we can ignore the file QLDoc requirement, but maybe we should add a QLDoc on the SimilarBlock class just saying DEPRECATED: This class is no longer used. or something similar.

And finally, we need to include a change note in https://github.com/github/codeql/tree/main/cpp/ql/src/change-notes.

[jketema]

I accidentally added an empty line between CodeDuplication::SimilarBlock and its documentation. That should be fixed now.

[MathiasVP]

I accidentally added an empty line between CodeDuplication::SimilarBlock and its documentation. That should be fixed now.

Oh, perfect.

[jketema]

The change note should be about the deprecation of the classes?

[MathiasVP]

The change note should be about the deprecation of the classes?

Yeah, exactly.

[MathiasVP]

LGTM!