render table .info in create table, also fix typing for rewriter

[zzzeek]

Discussed in #1328

^{Originally posted by BayerSe October 19, 2023}
Hi,

our Oracle db requires partitions for some of the tables, which we used to add using alembic with the following steps. These are based on the proposal of @zzzeek here (for nicer formatting see here).

It's been a long time since I needed a change in the schema, so I only now realized that there seems to have been a regression / change in behavior.

Main code:

from sqlalchemy import MetaData, Column, String
from sqlalchemy.ext.declarative import declarative_base

metadata = MetaData()
Base = declarative_base(metadata=metadata)


class Table(Base):
    __tablename__ = 'Table'
    name = Column(String(10), primary_key=True)
    __table_args__ = {'info': {'oracle_partition': "PARTITION BY ..."}}

This rewriter is added as process_revision_directives of context.configure in env.py with the goal of adding the info dict to the create_table statement:

writer = rewriter.Rewriter()

@writer.rewrites(ops.CreateTableOp)
def add_info_to_table(context, revision, op):
    op.kw["info"] = op.columns[0].table.info
    return ops.CreateTableOp(
            table_name=op.table_name,
            columns=op.columns,
            schema=op.schema,
            _namespace_metadata=op._namespace_metadata,
            _constraints_included=op._constraints_included,
            **op.kw,
        )

We add this to the migration scripts, which adds the partition command to the created statement:

import sqlalchemy as sa
from alembic import op
import textwrap

@sa.ext.compiler.compiles(sa.schema.CreateTable, "oracle")
def _add_suffixes(element, compiler, **kw):  # type: ignore
    text = compiler.visit_create_table(element, **kw)
    if "oracle_partition" in element.element.info:
        text += textwrap.dedent(element.element.info["oracle_partition"]).strip()
    return text

For alembic==1.6.5 and sqlalchemy==1.3.24 this result in the following auto-generated update command:

op.create_table(
    "Table",
    sa.Column("name", sa.String(length=10), nullable=False),
    sa.PrimaryKeyConstraint("name"),
    info={"oracle_partition": "PARTITION BY ..."},
)

However, for alembic==1.12.0 and sqlalchemy==2.0.22, the info is not added anymore, i.e. I just get

op.create_table(
    "Table",
    sa.Column("name", sa.String(length=10), nullable=False),
    sa.PrimaryKeyConstraint("name"),
)

I checked version alembic==1.7.0 as well, it broke between 1.6.5 and 1.7.0. In the changelog I found this comment, could that be related?

Thanks and regards
Sebastian

[sqla-tester]

Mike Bayer has proposed a fix for this issue in the main branch:

render .info in create_table https://gerrit.sqlalchemy.org/c/sqlalchemy/alembic/+/4930