column info doesnt register in alembic autogenerated migrations about sqlalchemy-redshift HOT 5 OPEN

I think this is an alembic bug. @zzzeek?

from sqlalchemy-redshift.

alembic's autogenerate render does not currently render the info dictionary. SQLA itself doesn't use .info at all so is not part of what it needs to render column DDL. However, if redshift and other dialects are relying upon info for extra DDL hints, that is a supported case so alembic should support rendering .info. A fix for this though should include .info for everything, columns, tables, indexes, etc. It also should be careful not to barf if there are un-reprable things in that .info dictionary (as any application can put any kind of object in this dictionary), and perhaps even only render simple ints, strings and booleans from the dictionary. this would take place in alembic/autogenerate/render.py and of course be exercised in new unit tests in tests/test_autogen_render.py.

I would note that alembic allows user-defined rendering right now, which would allow redshift to supply a workaround if this was worth it, but it would have to define the whole Column render itself: http://alembic.zzzcomputing.com/en/latest/api/runtime.html#alembic.runtime.environment.EnvironmentContext.configure.params.render_item probably not worth it.

from sqlalchemy-redshift.

@DanCardin @graingert @zzzeek
If you are still having this need (or if some people have it in the future) of auto-generating the alembic migration script for some Redshift tables with columns encoding.

Indeed it is currently not possible using Alembic but there is a workaround : write the migration script manually as following (using the example given by DanCardin)

def upgrade():
    from tables.models.example import Example
    Example.__table__.create(bind=op.get_bind())

Using this trick you avoid Alembic's code generation and use directly the sqlalchemy-redshift adaptor which itself is aware of the info={'encode': 'lzo'} field and will include it while creating the table.

from sqlalchemy-redshift.

from sqlalchemy-redshift.

Using @zzzeek 's suggested workaround, this renderer was sufficient for including info dicts in Redshift migrations.

def render_redshift_column(type_, col, autogen_context):
    """Render columns with info dicts for Redshift migrations."""
    if type_ == "column":
        render = "sa.Column("
        render += "'{name}'".format(name=col.name)
        render += ", sa.{coltype}".format(coltype=repr(col.type))
        render += ", nullable={null}".format(null=str(col.nullable))
        render += ", info={info})".format(info=str(col.info))
        return render
    else:
        return False

from sqlalchemy-redshift.