Schema generation enhancements

Piccolo now has a command for generating a schema from an existing database.

piccolo schema generate

The current implementation doesn’t cover every possible edge case and database feature, so there’s room for improvement. For example:

Column defaults

Getting the defaults for a column, and reflecting them in the Piccolo column. For example, if the column has a default of 1 in the database, we want that to be reflected in the Piccolo schema as:

class MyTable(Table):
    my_column = Integer(default=1)

On Delete / On Update

The database values aren’t currently reflected in the ForeignKey column definitions.

class MyTable(Table):
    my_column = ForeignKey(on_delete=OnDelete.cascade)

Decimal precision

The precision of a decimal column in the database currently isn’t reflected in the Decimal column definitions.

class MyTable(Table):
    my_column = Decimal(digits=(5,2))

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It’s a fairly beginner friendly feature to work on, because even though the code is fairly advanced, it’s completely self contained, and doesn’t require extensive knowledge of the rest of Piccolo.

[dantownsend]

@wmshort Yeah, it was just omitted because we didn’t have the reflection capabilities at the time.

[dantownsend]

@wmshort Good question - it looks like you can find ON DELETE and ON UPDATE here:

select * from information_schema.referential_constraints;

I found this gist on it:

https://gist.github.com/velosipedist/7250141