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from __future__ import with_statement |
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from alembic import context |
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from sqlalchemy import engine_from_config, pool |
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from logging.config import fileConfig |
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import logging |
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# this is the Alembic Config object, which provides |
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# access to the values within the .ini file in use. |
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config = context.config |
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# Interpret the config file for Python logging. |
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# This line sets up loggers basically. |
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fileConfig(config.config_file_name) |
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logger = logging.getLogger('alembic.env') |
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# add your model's MetaData object here |
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# for 'autogenerate' support |
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# from myapp import mymodel |
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# target_metadata = mymodel.Base.metadata |
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from flask import current_app |
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config.set_main_option('sqlalchemy.url', |
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current_app.config.get('SQLALCHEMY_DATABASE_URI')) |
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target_metadata = current_app.extensions['migrate'].db.metadata |
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# other values from the config, defined by the needs of env.py, |
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# can be acquired: |
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# my_important_option = config.get_main_option("my_important_option") |
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# ... etc. |
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def run_migrations_offline(): |
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"""Run migrations in 'offline' mode. |
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This configures the context with just a URL |
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and not an Engine, though an Engine is acceptable |
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here as well. By skipping the Engine creation |
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we don't even need a DBAPI to be available. |
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Calls to context.execute() here emit the given string to the |
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script output. |
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""" |
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url = config.get_main_option("sqlalchemy.url") |
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context.configure(url=url) |
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with context.begin_transaction(): |
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context.run_migrations() |
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def run_migrations_online(): |
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"""Run migrations in 'online' mode. |
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In this scenario we need to create an Engine |
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and associate a connection with the context. |
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""" |
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# this callback is used to prevent an auto-migration from being generated |
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# when there are no changes to the schema |
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# reference: http://alembic.readthedocs.org/en/latest/cookbook.html |
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def process_revision_directives(context, revision, directives): |
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if getattr(config.cmd_opts, 'autogenerate', False): |
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script = directives[0] |
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if script.upgrade_ops.is_empty(): |
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directives[:] = [] |
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logger.info('No changes in schema detected.') |
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engine = engine_from_config(config.get_section(config.config_ini_section), |
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prefix='sqlalchemy.', |
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poolclass=pool.NullPool) |
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connection = engine.connect() |
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context.configure(connection=connection, |
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target_metadata=target_metadata, |
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process_revision_directives=process_revision_directives, |
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**current_app.extensions['migrate'].configure_args) |
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try: |
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with context.begin_transaction(): |
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context.run_migrations() |
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finally: |
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connection.close() |
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if context.is_offline_mode(): |
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run_migrations_offline() |
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else: |
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run_migrations_online() |
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