Implement SQLite alter/rename/drop column via workarounds

[andrew]

Currently these just raise exceptions in the SQLite commands, but it would be nice to have these "just work", using workarounds like ​http://grass.osgeo.org/wiki/Sqlite_Drop_Column

[andrew]

Looks like this will require manually parsing the content of sqlite_master, which is not a feature I'm willing to roll in to 0.4 at this point. Pushing to The Future.

At this rate, 0.5 will be the parsing-a-plenty release.

[Robert <trebor74hr@…>]

What is suggested on page ​http://grass.osgeo.org/wiki/Sqlite_Drop_Column
is very similar what is already done and obviously works in ​django-evolution. Place is db.sqlite3.EvolutionOperations?.delete_column i.e.
​http://code.google.com/p/django-evolution/source/browse/trunk/django_evolution/db/sqlite3.py#9.

Basically:

• dump data to new temp table without the column
• drop table
• create table without the column
• copy data from temp table
• drop temp table

Why not reuse the logic/code and enable this. Btw. this type of scenario is base for all kind of implementations where db engine doesn't support SQL DDL command (alter table, alter column, rename column, drop column, add column, etc.). Later most of unsupported operations for various engines could be implemented in the same manner.

[andrew]

The major problem with implementing this so far has, in fact, been in determining the schema of the new temp table - previously, it would have involved parsing of the only data SQLite gives you about tables (their CREATE TABLE statement).

Now, someone's working on doing it using the ORM. Updates to follow.

[angri]

patch which can do the trick

[angri]

It was not tested with every column type supported by django. But I think it is a good start and it may be usefull for somebody.

--
Anton Gritsay
anton@…

[diegobz@…]

Any news about this feature?

[andrew]

It's being worked on in a separate fork; rename_column was merged in a while ago, others weren't ready.

[Velmont]

So it'll get in the next release?

[andrew]

Hopefully. Can't say much more just yet.

[olau@…]

Hi, just hit this page via Google. Actually I just did this by hand - instead of creating a tmp table, you can just rename the old table to tmp and use that as source.

[andrew]

0.7 fixes this.