Helper functions for the alembic database migration package

alembic_helper.py

""" alembic_helper.py

Copyright (c) 2016 Jonathan M. Altman

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``build_tables()`` and ``remove_tables()`` both take in an ordered dict where the key is a table to
create and the value is a tuple of sqlAlchemy Column definitions
Sample input for build_tables/remove_tables
``table_defs = OrderedDict((
    ('user', (
        sa.Column(u'id', sa.BIGINT(), primary_key=True),
        sa.Column(u'first_name', sa.TEXT(), nullable=False),
        sa.Column(u'last_name', sa.TEXT(), nullable=False),
    )),
    ('user_item', (
        sa.Column(u'id', sa.BIGINT(), primary_key=True),
        sa.Column(u'user_id', sa.BIGINT(), sa.ForeignKey(u'user.id'), nullable=False),
        sa.Column(u'description', sa.TEXT(), nullable=False),
        sa.Column(u'this_allows_nulls', sa.TEXT()),
    )),
))``

Usage:
    ``build_tables(table_defs)`` to put the tables in in the order they appear in the ordered dict
    ``remove_tables(table_defs)`` to remove the tables in reverse order they appear in the ordered dict, to avoid FK issues
"""
from alembic import op
import sqlalchemy as sa

def build_tables(table_defs):
    for table_name, column_defs in table_defs.iteritems():
        op.create_table(table_name, *column_defs)


def remove_tables(table_defs):
    for table_name in reversed(table_defs.keys()):
        op.drop_table(table_name)