issue_comments

Failing test: python def test_extract_null_values(fresh_db): fresh_db["species"].insert({"id": 1, "species": "Wolf"}, pk="id") fresh_db["individuals"].insert_all( [ {"id": 10, "name": "Terriana", "species": "Fox"}, {"id": 11, "name": "Spenidorm", "species": None}, {"id": 12, "name": "Grantheim", "species": "Wolf"}, {"id": 13, "name": "Turnutopia", "species": None}, {"id": 14, "name": "Wargal", "species": "Wolf"}, ], pk="id", ) fresh_db["individuals"].extract("species") assert fresh_db["species"].schema == ( "CREATE TABLE [species] (\n" " [id] INTEGER PRIMARY KEY,\n" " [species] TEXT\n" ")" ) assert fresh_db["individuals"].schema == ( 'CREATE TABLE "individuals" (\n' " [id] INTEGER PRIMARY KEY,\n" " [name] TEXT,\n" " [species_id] INTEGER,\n" " FOREIGN KEY(species_id) REFERENCES species(id)\n" ")" ) assert list(fresh_db["species"].rows) == [ {"id": 1, "species": "Wolf"}, {"id": 2, "species": "Fox"}, ] assert list(fresh_db["individuals"].rows) == [ {"id": 10, "name": "Terriana", "species_id": 2}, {"id": 11, "name": "Spenidorm", "species_id": None}, {"id": 12, "name": "Grantheim", "species_id": 1}, {"id": 13, "name": "Turnutopia", "species_id": None}, {"id": 14, "name": "Wargal", "species_id": 1}, ]

Actually I think this should be an option to .extract() which controls if nulls are extracted or left alone. Maybe called extract_nulls=True/False.

Either way I think I'm going to need to add some SQL which uses where a = b or (a is null and b is null).

The alternative solution here would be that a single null value DOES get extracted. To implement this I would need to add some logic that uses is null instead of =.

How should this work with extractions covering multiple columns?

If there's a single column then it makes sense that a null value would not be extracted into the lookup table, but would instead become stay as null.

For a multiple column extraction, provided at least one of those columns is not null It should map to a record in the lookup table. Only if ALL of the extracted columns are null should the lookup value stay null.