Set default length on strings (varchar) for the mariadb dialect

[itsbekas]

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Example Code

from sqlmodel import SQLModel, create_engine, Field

class Hero(SQLModel, table=True):
    name: str = Field(primary_key=True)

database_url = 'mariadb+mariadbconnector://username:password@localhost:3306/testdb'
engine = create_engine(database_url)

SQLModel.metadata.create_all(engine)

Description

When using MariaDB, string fields don't have a default string size, which leads to the following error:

sqlalchemy.exc.CompileError: VARCHAR requires a length on dialect mariadb

#844 seems to be a similar issue but I think we're talking about different problems.

Operating System

Linux

Operating System Details

EndeavourOS

SQLModel Version

0.0.16

Python Version

3.11.8

Additional Context

No response

[itsbekas]

A pull request with a possible solution for this is now available in #882