Päringukäsitlus

Päringukäsitlus, often translated as query processing, refers to the sequence of operations a database management system (DBMS) performs to execute a user-initiated query. This process is crucial for retrieving the requested data efficiently and accurately.

The typical query processing lifecycle begins with parsing the query. The DBMS analyzes the query's syntax to ensure it conforms to the database's query language, such as SQL. Following parsing, the query is typically translated into an internal representation, often a logical plan. This plan describes the operations needed to retrieve the data without specifying how those operations will be physically executed.

Next, the query is optimized. This is a critical phase where the DBMS chooses the most efficient execution strategy from potentially many alternatives. Query optimizers consider various factors, including available indexes, data distribution, and the cost of different operations, to minimize execution time and resource consumption. The output of optimization is a physical execution plan.

Finally, the execution engine carries out the operations specified in the physical plan. This involves accessing the data from storage, performing necessary joins, filters, aggregations, and other operations, and returning the results to the user. The efficiency of query processing directly impacts the performance of database applications.