[Refactoring Plan]

[baiqiushi]

P1 Enriching test cases

• Driver: @colinthebomb1

P2 Refactoring the engine code to use internal new AST data structure

• [1] Define the new AST data structure, e.g., class node: {type:= {column, table, literal, operator}, alias: str, name: str, ...}
  • Driver: @HazelYuAhiru
• [2] SQL plain text -> mo_sql_parser -> qb_parser -> new AST structure -> qb_formatter -> mo_sql_formatter -> SQL plain text
• [3] Refactor query_rewriter;
• [4] Refactor rule_generator;