Creating revision for specific object

[Zac Goldstein]

Hello, I'm trying to create a revision programatically with the operations also made programatically. I've been trying this hackish approach below, which I now think probably isn't the right way to go due to the internals of AutogenContext, which seems required for rendering. 

Here's what I have so far:

    upgrade_ops = UpgradeOps([CreateTableOp.from_table(model.__table__)])

    downgrade_ops = DowngradeOps([DropTableOp.from_table(model.__table__)])

    command_args = dict(
        message="create table " + tname,
        autogenerate=False,
        sql=False,
        head="head",
        splice=False,
        branch_label=None,
        version_path=None,
        rev_id=rev_id(),
        depends_on=None

    )

    script_args = {k:v for k, v in command_args.items() if k != "sql" and k != "autogenerate"}
    migration_script = MigrationScript(upgrade_ops=upgrade_ops,
        downgrade_ops=downgrade_ops, **script_args)
    migration_script._needs_render = True

    ini_path = os.path.abspath(os.path.join(os.path.dirname(__file__), '../../../alembic.ini'))
    config = Config(ini_path, ini_section=table['schema'])
    script_directory=ScriptDirectory.from_config(config)
    revision = RevisionContext(config, script_directory, command_args)
    revision._last_autogen_context = SimpleNamespace(imports=set())
    revision._to_script(migration_script)

My other thought is to use EnvironmentContext and run a full automigration with include_object set to something like

lambda o: o is model.__table__

Doing the full automigration seems overkill, but if it's considerably easier then it's preferable. If I go this route It's not clear to me how to avoid env.py and instead run this other context with the new include_object.

Any help would be appreciated.

Zac

[Mike Bayer]

this should simplify things a bit

from sqlalchemy import Column
from sqlalchemy import Integer
from sqlalchemy import MetaData
from sqlalchemy import Table

from alembic.autogenerate import RevisionContext
from alembic.config import Config
from alembic.operations.ops import CreateTableOp
from alembic.operations.ops import UpgradeOps
from alembic.runtime.environment import EnvironmentContext
from alembic.script import ScriptDirectory
from alembic.util import rev_id

m = MetaData()
t = Table("some_table", m, Column("q", Integer), schema="foo")


command_args = dict(
message="create table " + t.name,

autogenerate=False,
sql=False,
head="head",
splice=False,
branch_label=None,
version_path=None,
rev_id=rev_id(),

depends_on=None,
)

config = Config("alembic.ini")
script_directory = ScriptDirectory.from_config(config)
revision_context = RevisionContext(config, script_directory, command_args)


with EnvironmentContext(
config, script_directory, template_args=revision_context.template_args
) as env:
env.configure(dialect_name="sqlite")
upgrade_ops = UpgradeOps([CreateTableOp.from_table(t)])
downgrade_ops = upgrade_ops.reverse()
revision_context.generated_revisions[0].upgrade_ops = upgrade_ops
revision_context.generated_revisions[0].downgrade_ops = downgrade_ops
revision_context.run_no_autogenerate(
command_args["rev_id"], env.get_context()
)

# generates the file
scripts = [script for script in revision_context.generate_scripts()]

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[Zac Goldstein]

fantastic, this worked like a charm.

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