How Does the Database Understand and Execute Your Query?

This post details the internal workings of Milvus's query execution engine. It explains how query expressions with scalar filtering are parsed using EBNF syntax, how an Abstract Syntax Tree (AST) is generated using ANTLR and the Expr package, and how the query is executed through a visitor design pattern on protobuf structures, resulting in a bitmask output. It also provides an example of a complex film query and its step-by-step processing.