Creating minimal POC code for testing op.create_table(), op.create_index(), etc.

[gordthompson]

I'd like to create a minimalist code example to test certain Alembic operations without a full-blown migration setup. I started with the following, fully expecting it to fail because it didn't address how to create the engine (e.g., what the connection URL is). Still, I thought I'd try it to see what failed.

from alembic import op
import sqlalchemy as sa

op.create_table(
    "invoice",
    sa.Column("invoice_number", sa.Integer(), nullable=False),
    sa.Column("account_number", sa.Integer(), nullable=True),
    sa.PrimaryKeyConstraint("invoice_number"),
)
op.create_index(op.f("ix_invoice_account_number"), "invoice", ["account_number"], unique=False)

The error is

Traceback (most recent call last):
  File "<string>", line 5, in create_table
NameError: name '_proxy' is not defined

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/gord/git/sqlalchemy-cockroachdb/.gord_stuff/alembic_op.py", line 4, in <module>
    op.create_table(
  File "<string>", line 7, in create_table
  File "/home/gord/git/sqlalchemy-cockroachdb/.venv/lib/python3.9/site-packages/alembic/util/langhelpers.py", line 136, in _name_error
    raise NameError(
NameError: Can't invoke function 'create_table', as the proxy object has not yet been established for the Alembic 'Operations' class.  Try placing this code inside a callable.
Traceback (most recent call last):
  File "<string>", line 5, in create_table
NameError: name '_proxy' is not defined

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/gord/git/sqlalchemy-cockroachdb/.gord_stuff/alembic_op.py", line 4, in <module>
    op.create_table(
  File "<string>", line 7, in create_table
  File "/home/gord/git/sqlalchemy-cockroachdb/.venv/lib/python3.9/site-packages/alembic/util/langhelpers.py", line 136, in _name_error
    raise NameError(
NameError: Can't invoke function 'create_table', as the proxy object has not yet been established for the Alembic 'Operations' class.  Try placing this code inside a callable.

My hope is to jury-rig an environment that is sufficiently Alembic-aware to run relatively simple operations on a third-party dialect without creating formal migrations. Can anyone suggest a place to start?

[zzzeek]

you can run operations against any engine using the short example that's at https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations

from alembic.migration import MigrationContext
from alembic.operations import Operations

myengine = create_engine(whatever)

conn = myengine.connect()


ctx = MigrationContext.configure(conn)
op = Operations(ctx)

op.alter_column("t", "c", nullable=True)