[SQLite]

The TH3 test harness for SQLite (https://www.sqlite.org/th3.html) supports a virtual filesystem in which we can create test database files that appear to be very large but that don't actually contain much data or use much space.

We also have a simple utility program in the SQLite source tree (https://www.sqlite.org/src/file/tool/enlargedb.c) that lets you create a massive database file using a sparse file (https://en.wikipedia.org/wiki/Sparse_file) on systems that support that kind of thing.