issue_comments

Ha, yes, I might end up making something very niche. That's OK.

I'm building a UI for Datasette that lets users make schema changes, so it's important to me that the tool work in a non-surprising way -- if you ask for a column of type X, you should get type X. If the column or table previously had CHECK constraints, they shouldn't be silently removed. And so on. I had hoped that I could just lean on sqlite-utils, but I think it's a little too surprising.

I think the bigger issue is that sqlite-utils mixes mechanism (it implements the 12-step way to alter SQLite tables) and policy (it has an opinionated stance on what column types should be used).

That might be a design choice to make it accessible to users by providing a reasonable set of defaults, but it doesn't quite fit my use case.

It might make sense to extract a separate library that provides just the mechanisms, and then sqlite-utils would sit on top of that library with its opinionated set of policies.

That would be a very big change, though.

I might take a stab at extracting the library, but just for the table schema migration piece, not all the other features that sqlite-utils supports. I wouldn't expect sqlite-utils to depend on it.

Part of my motivation is that I want to provide some other abilities, too, like support for CHECK constraints. I see that the issue in this repo (https://github.com/simonw/sqlite-utils/issues/358) proposes a bunch of short-hand constraints, which I wouldn't want to accidentally expose to people -- I want a layer that is a 1:1 mapping to SQLite.

I'd support that, but I'm not the author of this library.

One challenge is that would be a breaking change. Do you see a way to enable it without affecting existing users or bumping the major version number?

Ah, it looks like that is controlled by this dict: https://github.com/simonw/sqlite-utils/blob/main/sqlite_utils/db.py#L178

I suspect you could overwrite the datetime entry to achieve what you want

I think it's not currently possible: sqlite-utils requires that it be one of integer, text, float, blob (see code)

IMO, this is a bit of friction and it would be nice if it was more permissive. SQLite permits developers to use any data type when creating a table. For example, this is a perfectly cromulent sqlite session that creates a table with columns of type baz and bar:

``` sqlite> create table foo(column1 baz, column2 bar); sqlite> .schema foo CREATE TABLE foo(column1 baz, column2 bar); sqlite> select * from pragma_table_info('foo'); cid name type notnull dflt_value pk

0 column1 baz 0 0
1 column2 bar 0 0
```

The idea is that the application developer will know what meaning to ascribe to those types. For example, I'm working on a plugin to Datasette. Dates are tricky to handle. If you have some existing rows, you can look at the values in them to know how a user is serializing the dates -- as an ISO 8601 string? An RFC 3339 string? With millisecond precision? With timezone offset? But if you don't yet have any rows, you have to guess. If the column is of type TEXT, you don't even know that it's meant to hold a date! In this case, my plugin will look to see if the column is of type DATE or DATETIME, and assume a certain representation when writing.

Perhaps there is an argument that sqlite-utils is trying to conform to SQLite's strict mode, and that is why it limits the choices. In strict mode, SQLite requires that the data type be one of INT, INTEGER, REAL, TEXT, BLOB, ANY. But that can't be the case -- sqlite-utils supports FLOAT, which is not one of the valid types in strict mode, and it rejects INT, REAL and ANY, which are valid.

That said, it looks like the check is only enforced at the CLI level. If you use the API directly, I think it'll work.