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from flask import current_app
from alembic import context
from sqlalchemy import text
import logging
# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config
def get_engine():
try:
# this works with Flask-SQLAlchemy<3 and Alchemical
return current_app.extensions['migrate'].db.get_engine()
except TypeError:
# this works with Flask-SQLAlchemy>=3
return current_app.extensions['migrate'].db.engine
def get_engine_url():
try:
return get_engine().url.render_as_string(hide_password=False).replace(
'%', '%%')
except AttributeError:
return str(get_engine().url).replace('%', '%%')
# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
config.set_main_option('sqlalchemy.url', get_engine_url())
target_db = current_app.extensions['migrate'].db
# other values from the config, defined by the needs of env.py,
# can be acquired:
# my_important_option = config.get_main_option("my_important_option")
# ... etc.
def get_metadata():
if hasattr(target_db, 'metadatas'):
return target_db.metadatas[None]
return target_db.metadata
def run_migrations_offline():
"""Run migrations in 'offline' mode.
This configures the context with just a URL
and not an Engine, though an Engine is acceptable
here as well. By skipping the Engine creation
we don't even need a DBAPI to be available.
Calls to context.execute() here emit the given string to the
script output.
"""
url = config.get_main_option("sqlalchemy.url")
context.configure(
url=url, target_metadata=get_metadata(), literal_binds=True
)
with context.begin_transaction():
context.run_migrations()
def run_migrations_online():
"""Run migrations in 'online' mode.
In this scenario we need to create an Engine
and associate a connection with the context.
"""
# this callback is used to prevent an auto-migration from being generated
# when there are no changes to the schema
# reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
def process_revision_directives(context, revision, directives):
if getattr(config.cmd_opts, 'autogenerate', False):
script = directives[0]
if script.upgrade_ops.is_empty():
directives[:] = []
logging.info('No changes in schema detected.')
connectable = get_engine()
with connectable.connect() as connection:
context.configure(
connection=connection,
target_metadata=get_metadata(),
process_revision_directives=process_revision_directives,
**current_app.extensions['migrate'].configure_args
)
with context.begin_transaction():
bind = context.get_bind()
if bind.engine.name == 'sqlite':
bind.execute(text("PRAGMA foreign_keys=OFF;"))
elif bind.engine.name == 'postgresql':
bind.execute(text("SET CONSTRAINTS ALL DEFERRED;"))
context.run_migrations()
if bind.engine.name == 'sqlite':
bind.execute(text("PRAGMA foreign_keys=ON;"))
elif bind.engine.name == 'postgresql':
bind.execute(text("SET CONSTRAINTS ALL IMMEDIATE;"))
if context.is_offline_mode():
run_migrations_offline()
else:
run_migrations_online()
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