issue_comments

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

I've got your concern. Let's see if we will be replied on it and i'll close the issue some later.

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.

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

And thank you for pointing me to it. At least, i can make a monkey patch for my need...

Isn't your suggestion too fundamental for the utility?

The bigger flexibility, the bigger complexity. Your idea make sense defenitely, but how often do you make schema changes? And how many people could benefit from it, what do you think?

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.

Do you see a way to enable it without affecting existing users or bumping the major version number?

I don't see a clean solution, only extending code with a side variable that tells us we want to apply advanced types instead of basic.

it could be a similiar command like tranform-v2 --type column DATETIME or a cli option transform --adv-type column DATETIME along with a dict that contains the advanced types. Then with knowledge that we run an advanced command we take that dictionary somehow, we can wrap the current and new dictionaries by a superdict and work with it everywhere according to the knowledge. This way shouldn't affect users who are using the previous lib versions and it have to be merged in the next major one.

But this way looks a bad design, too messy.

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?

I could, of course.

Doest it worth bringing such the improvement to the library?

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

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.

It works, but a column becomes TEXT

```python In [1]: import sqlite_utils In [2]: db = sqlite_utils.Database('events.sqlite') In [3]: table = db['cards.chunk.get'] In [4]: table.columns_dict Out[4]: {'id': int, 'timestamp': float, 'data_chunk_number': int, 'user_id': str, 'meta_duplication_source_id': int, 'context_sort_attribute': str, 'context_sort_order': str}

In [5]: from datetime import datetime In [7]: table.transform(types={'timestamp': datetime}) In [8]: table.columns_dict Out[8]: {'id': int, 'timestamp': str, 'data_chunk_number': int, 'user_id': str, 'meta_duplication_source_id': int, 'context_sort_attribute': str, 'context_sort_order': str} ```

bash ❯ sqlite-utils schema events.sqlite cards.chunk.get CREATE TABLE "cards.chunk.get" ( [id] INTEGER PRIMARY KEY NOT NULL, [timestamp] TEXT, ...