Even SQLite3 does this. https://www.sqlite.org/queryplanner.html https://www.sqlite.org/queryplanner.html says under "Sorting": > Furthermore, the entire outpu

Even SQLite3 does this. https://www.sqlite.org/queryplanner.html https://www.sqlite.org/queryplanner.html says under "Sorting": > Furthermore, the entire output is accumulated in temporary storage (which might be either in main memory or on disk, depending on various compile-time and run-time settings) which can mean that a lot of temporary storage is required to complete the query. It also will sometimes create an index during a query. https://www.sqlite.org/tempfiles.html https://www.sqlite.org/tempfiles.html mentions this under "Transient Indices".