Reason for this bug is this code in sub fingerprint:

It does not care if escaped quoted is in the end of the argument or not. However, slow query log can easily contain records like:

Reason for this bug is double slash in the end of the search string. It will be repeatable with any query like:

However for

It generates:

which is even worse.

To:
CC:

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Having a clear way to reproduce it, I think it is enough.
I can write instructions for QA after working on this ticket.

As per Sveta's request am providing the exact steps for reproducing:

Then check file content (output is large), but pay attention to ~2nd line where it says:

On bugged case:

On non bugged case: