postgresql ExcludeConstraint behave differently with --autogenerate compare to sqlalchemy Base.metadata.create_all

[tc-yu]

Describe the bug
when running alembic revision --autogenerate, on a table with

ExcludeConstraint(
    (func.tstzrange(effective_time, expiry_time), "&&"),
    using="gist",
)

it generates

    postgresql.ExcludeConstraint(('tstzrange(effective_time, expiry_time)', '&&'), using='gist'),

in the revision script, resulting in sqlalchemy.exc.ConstraintColumnNotFoundError: Can't create ExcludeConstraint on table 'time_slot': no column named 'tstzrange(effective_time, expiry_time)' is present.

Adding sqlalchemy.text around the string does fix the issue

Expected behavior
the table definition works with sqlalchemy's Base.metadata.create_all(bind=engine), creating

"time_slot_tstzrange_excl" EXCLUDE USING gist (tstzrange(effective_time, expiry_time) WITH &&)

in the database so I expect it works the same in alembic

To Reproduce

I setup a minimal example in this repo: https://github.com/tc-yu/alembic-pgsql-tztsrange

model:

from datetime import datetime

from sqlalchemy import DateTime, Identity, func
from sqlalchemy.dialects.postgresql import ExcludeConstraint
from sqlalchemy.orm import Mapped, declarative_base, mapped_column

class TimeSlot(Base):
    __tablename__ = "time_slot"

    id: Mapped[int] = mapped_column(Identity(), primary_key=True)

    effective_time: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), index=True
    )
    expiry_time: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), index=True
    )

    __table_args__ = (
        ExcludeConstraint(
            (func.tstzrange(effective_time, expiry_time), "&&"),
            using="gist",
        ),
    )

Error

sqlalchemy.exc.ConstraintColumnNotFoundError: Can't create ExcludeConstraint on table 'time_slot': no column named 'tstzrange(effective_time, expiry_time)' is present.

Versions.

• OS: macOS
• Python: 3.11.3
• Alembic: 1.10.4
• SQLAlchemy: 2.0.11
• Database: postgresql 15.2
• DBAPI: psycopg 3.1.8

Additional context
This is the first time I work with ExcludeConstraint, so it might just be me using the wrong way to define it in the model

Have a nice day!

[CaselIT]

Hi,

Thanks for reporting.

[sqla-tester]

Federico Caselli has proposed a fix for this issue in the main branch:

Fix ExcludeConstraint with func. https://gerrit.sqlalchemy.org/c/sqlalchemy/alembic/+/4591