Historically Debezium was adding MariaDB syntax differences into our copy of MySQL grammar. Currently we have a dedicated MariaDB connector so it is no longer necessary and we should align with upstream grammar as much as possible.
Also there was a major reformatting of upstream grammars in the past which means that backporting of fixes is now more complicated. To simplify the future maintenance we should

• Format our grammar with the same tool as upstream grammar
• Compare the grammars and remove MariaDB specific extensions that are not in upstream MySQL grammar
• Make sure all these extensions are properly handled in MariaDB grammar
• Keep current set of tests to verify that our grammar is still compatible with all changes we introduced

The expected end result is

• MariaDB grammar is the same as the upstream grammar
• MariaDB tests are the same as the upstream grammar
• MySQL grammar contains only Percona extensions - this is only difference from upstream grammar
• MySQL grammar tests will be replaced with the upstream ones. The extra test statments in our grammar not covered in upstream grammar test will be moved to separate file and kept for regression testing