SQL Engine - SQL processing (Sql Compiler)

Parsing

SQL Engine - SQL Parser

Optimization

SQL Engine - Query Optimizer (Query Optimization)

Query optimization is the process of choosing the most efficient means of executing a SQL statement. The database optimizes queries based on the optimizer statistics collected about the actual data being accessed.

The optimizer uses statistics such as :

• the number of rows,
• the size of the data set,
• and other factors

to generate possible execution plans,

• assigning a numeric cost to each plan.

The database uses the plan with the lowest cost.

Row Source Generation

SQL Engine - Row source generator

Execution

SQL Engine - Execution