kratosst / eva-src

Source code of EVA system

System Workflow

• server - System launches and emits client commands to command handler.
• parser - System parses SQL and converts it to statement.
• It mainly generates CREATE, SELECT, INSERT, and LOAD, etc statements.
• For SELECT statement, some tokens are direclty mapped to expressions(expression). E.g., UDF is mapped to function expression.
• optimizer / statement_to_opr_convertor.py - System converts a statement to an operator represented in tree structure(optimizer / operators.py).
• For statements other than SELECT, it is mostly one - to - one mapping from statement to operator.
• For SELECT statement, it is expanded to different operators PROJECT and FILTER, etc.
• optimizer / plan_generator.py - System runs query optimization first.
• All operators in the tree are converted to group expression for optimization(optimizer / group_expression.py).
• Apply rewrite based on rules(optimizer / rules).
• optimizer / plan_generator.py - System builds physical plans(planner) based on the optimal logical plan.
• executor - System executes the physical plans.