Support for generated columns

This is a fairly new feature – SQLite version 3.31.0 (2020-01-22) – that I, admittedly, haven’t gotten to work yet. But it looks incredibly useful: https://dgl.cx/2020/06/sqlite-json-support

I’m not sure if this is an option on add-column or a separate command like add-generated-column. Either way, it needs an argument to populate it. It could be something like this:

sqlite-utils add-column data.db table-name generated --as 'json_extract(data, "$.field")' --virtual

More here: https://www.sqlite.org/gencol.html

[simonw]

Two new parameters to .create_table() and friends:

• generated={...} - generated column definitions
• generated_stored={...} generated stored column definitions

These columns will be added at the end of the table, but you can use the column_order= parameter to apply a different order.

[simonw]

Trying to figure out what that extra field in table_info compared to table_xinfo is:

>>> list(db.query("PRAGMA table_xinfo('t')"))
[{'cid': 0,
  'name': 'body',
  'type': 'TEXT',
  'notnull': 0,
  'dflt_value': None,
  'pk': 0,
  'hidden': 0},
 {'cid': 1,
  'name': 'd',
  'type': 'INT',
  'notnull': 0,
  'dflt_value': None,
  'pk': 0,
  'hidden': 2}]
``
Presumably `hidden` 0 v.s 2 v.s. other values has meaning.