On 08/30/2016 10:52 PM, [email protected] wrote:
I am using PostgreSQL and Alembic for migration. When I added new column
to my User table Alembic generated migration with the following script:
from alembic import op
import sqlalchemy as sa
import random
def generate_toke():
return random.random()
def upgrade():
op.add_column('user', sa.Column('token', sa.String(), nullable=True ))
op.execute('some code here')
What I actually want to do is autogenerating the value of token by the
generate_toke function for existing data in my DB.
Is there a solution?
Because this is a Python function, simplest way to run the actual
function (which might not be necessary, see below), run an update()
statement in a loop:
from sqlalchemy import Table, MetaData, select
# make a local Table object
user_table = Table(
'user', MetaData(),
# whatever the primary key is goes here, for example "user_id"
Column('user_id', Integer, primary_key=True),
# then your token column
Column('token', String())
)
connection = op.get_bind()
for row in connection.execute(select([user_table.c.user_id])):
connection.execute(
user_table.update().
values(token=generate_token()).
where(user_table.c.id == row['user_id'])
)
now, if the function is truly the "random()" function, good news.
Postgresql has that already. So instead of all the above, just do:
op.execute("update user set token=random()")
Alembic`s onwer Michael Bayer redirect me there
https://bitbucket.org/zzzeek/alembic/issues/383/set-the-value-of-column-when-upgrading
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