Known differences

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1. FerretDB uses the same protocol error names and codes, but the exact error messages may be different in some cases.
2. FerretDB does not support NUL (\0) characters in strings.
3. FerretDB does not support nested arrays.
4. FerretDB converts -0 (negative zero) to 0 (positive zero).
5. Document restrictions:
   • document keys must not contain . sign;
   • document keys must not start with $ sign;
   • document fields of double type must not contain Infinity, -Infinity, or NaN values.
6. When insert command is called, insert documents must not have duplicate keys.
7. Update command restrictions:
   • update operations producing Infinity, -Infinity, or NaN are not supported.
8. Database and collection names restrictions:
   • name cannot start with the reserved prefix _ferretdb_;
   • database name must not include non-latin letters;
   • collection name must be valid UTF-8 characters;
9. FerretDB offers the same validation rules for the scale parameter in both the collStats and dbStats commands. If an invalid scale value is provided in the dbStats command, the same error codes will be triggered as with the collStats command.

If you encounter some other difference in behavior, please join our community to report a problem.