Query Processor The query processor components include: DDL interpreter--interprets DDL statements and records the definitions in the data dictionary. DML compiler--translates DML statements in a query language into an evaluation plan consisting of low-level instructions that the query evaluation engine understands. The DML compiler performs query optimization;that is,it picks the lowest cost evaluation plan from among the various alternatives. Query evaluation engine--executes low-level instructions generated by the DML compiler. Database System Concepts-7th Edition 1.25 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 1.25 ©Silberschatz, Korth and Sudarshan th Edition Query Processor ▪ The query processor components include: • DDL interpreter -- interprets DDL statements and records the definitions in the data dictionary. • DML compiler -- translates DML statements in a query language into an evaluation plan consisting of low-level instructions that the query evaluation engine understands. ▪ The DML compiler performs query optimization; that is, it picks the lowest cost evaluation plan from among the various alternatives. • Query evaluation engine -- executes low-level instructions generated by the DML compiler