When a query is to be executed, a query plan is used by the database to forge a data path where the best and the most efficient types of routes are created. If there are table join, indexes, and a number of rows in the tables, a variety of mathematical calculations using different algorithms are prepared. Having an execution plan is useful when there are issues with SQL, and to debug multiple table joins and index setups, and follow a path to solve a data or programming issue.
Apart from the straightforward SQL statements in a plain format, there will be those statements that will be used within iOS and wrapped in one of the languages such as Objective-C or Swift.
When the query execution plan is executed, the data, the information, is geared for debugging only and should be used as guidance. Every SQLite release will have different updates that affect the product. The whole idea of a plan is to outline the strategy path an SQL command takes.