Generated colums in SQLite are described this way in [the docs](https://www.sqlite.org/gencol.html):
> Generated columns (also sometimes called "computed columns") are columns of a table whose values are a function of other columns in the same row. Generated columns can be read, but their values can not be directly written. The only way to change the value of a generated column is to modify the values of the other columns used to calculate the generated column.
I found them from [this blog post](https://antonz.org/json-virtual-columns/), which explains how to use a generated column and index to efficiently query on the contents of a JSON column in SQLite. I found that blog post from [this Reddit comment](https://www.reddit.com/r/sqlite/comments/xcnggj/comment/io8840p/).
Depends on D12740