What is a generic way of getting more decimals for a datetime instead of using mysql DATETIME fsp?

[MathijsNL]

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Example Code

from datetime import datetime, timezone
from typing import Optional

from sqlalchemy import Column, text
from sqlalchemy.dialects import mysql
from sqlalchemy.sql import func
from sqlmodel import Field, Session, SQLModel, create_engine, select

db_user = "root"
db_pass = ""
db_host = "localhost"
db_name = "testdb"

class TestClass(SQLModel, table=True):

    __tablename__ = "testtable"

    id: Optional[int] = Field(default=None, primary_key=True)

    # datetime without decimals
    date_time: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))

    # mysql DATETIME with 3 decimals
    date_time_fsp: datetime = Field(
        sa_column=Column(
            mysql.DATETIME(fsp=3), server_default=func.utc_timestamp(3), nullable=False
        )
    )


init_engine = create_engine(
    f"mysql+mysqldb://{db_user}:{db_pass}@{db_host}/", echo=True
)

with init_engine.connect() as connection:
    connection.execute(text(f"CREATE DATABASE IF NOT EXISTS {db_name}"))

engine = create_engine(f"mysql+mysqldb://root:{db_pass}@localhost/{db_name}", echo=True)

SQLModel.metadata.create_all(engine)
session = Session(engine)

session.add(TestClass())
session.commit()

with Session(engine) as session:
    statement = select(TestClass)
    results = session.exec(statement)
    for hero in results:
        print(hero)


session.close()

Description

I can't figure out how to get a higher time precision in a generic way. If possible I would like to prevent dialect specific workarounds. So in short, what do I need to do differently to get a date_time column with decimals:

date_time: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.22

Python Version

Python 3.12.7

Additional Context

No response

[Sammyjroberts]

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