issue_comments

In working on this I learned that rowid values in SQLite are way less stable than I had thought - in particular, they are often entirely rewritten on a VACUUM:

https://www.sqlite.org/lang_vacuum.html#how_vacuum_works

The VACUUM command may change the ROWIDs of entries in any tables that do not have an explicit INTEGER PRIMARY KEY.

So this fix wasn't as valuable as I thought. I need to move away from ever assuming that a rowid is a useful foreign key for anything.

Yes! That recreated the bug: ```

  assert previous_rows == next_rows

E AssertionError: assert equals failed E [ [
E (1, '1', 'Paris'), (1, '1', 'Paris'),
E (3, '3', 'New York'), (2, '3', 'New York'),
E (4, '4', 'London'), (3, '4', 'London'),
E ] ... E
```

Oh! Maybe the row ID preservation here is a coincidence because the tables are created from scratch and count 1, 2, 3.

If I delete a row from the table and then insert some more - breaking the rowid sequence - it might show the bug.

I just noticed that the table where I encountered this bug wasn't actually a rowid table after all - it had an id column that was a text primary key.

The reason the rowid was important is that's how the FTS mechanism in Datasette relates FTS entries to their rows.

But I tried this test and it passed, too: python def test_transform_preserves_rowids(fresh_db): fresh_db["places"].insert_all( [ {"id": "1", "name": "Paris", "country": "France"}, {"id": "2", "name": "London", "country": "UK"}, {"id": "3", "name": "New York", "country": "USA"}, ], pk="id", ) previous_rows = list( tuple(row) for row in fresh_db.execute("select rowid, id, name from places") ) # Transform it fresh_db["places"].transform(column_order=("country", "name")) # Should be the same next_rows = list( tuple(row) for row in fresh_db.execute("select rowid, id, name from places") ) assert previous_rows == next_rows

I tried bumping that up to 10,000 rows instead of just 3 but the test still passed.

That's odd, I wrote a test for this just now and it passes already: python def test_transform_preserves_rowids(fresh_db): # Create a rowid table fresh_db["places"].insert_all( ( {"name": "Paris", "country": "France"}, {"name": "London", "country": "UK"}, {"name": "New York", "country": "USA"}, ), ) assert fresh_db["places"].use_rowid previous_rows = list( tuple(row) for row in fresh_db.execute("select rowid, name from places") ) # Transform it fresh_db["places"].transform(column_order=("country", "name")) # Should be the same next_rows = list( tuple(row) for row in fresh_db.execute("select rowid, name from places") ) assert previous_rows == next_rows So maybe I'm wrong about the cause of that bug?