How to implement a composite primary key

[jaohbib]

First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the SQLModel documentation, with the integrated search.
• I already searched in Google "How to X in SQLModel" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to SQLModel but to Pydantic.
• I already checked if it is not related to SQLModel but to SQLAlchemy.

Commit to Help

• I commit to help with one of those options 👆

Example Code

class test(SQLModel, table=True):
     src_ppn: str = Field(primary_key=True)
     dst_ppn: str  = Field(primary_key=True)
   
     __table_args__ = (
         PrimaryKeyConstraint(src_ppn, dst_ppn),
     )

Description

I want to create a table containing a composite primary key
I recive the following error

ArgumentError: String column name or column expression for DDL constraint expected, got FieldInfo(annotation=NoneType, required=True).

Operating System

Linux

Operating System Details

Ubuntu 22.04

SQLModel Version

0.0.22

Python Version

3.9.7

Additional Context

No response

[monchin]

I guess there's something wrong with PrimaryKeyConstraint. You csn try to remove it like the example in the document

[acidnik]

in case someone landed here from the search engine, i think the problem could be fixed like this:

     __table_args__ = (
         PrimaryKeyConstraint("src_ppn", "dst_ppn"), # note the quotes around fields
     )

[YuriiMotov]

You don't actually need PrimaryKeyConstraint.
Just specifying primary_key=True for both fields is enough to create composite primary key:

from sqlalchemy import PrimaryKeyConstraint
from sqlmodel import SQLModel, Field, create_engine


class test(SQLModel, table=True):
    src_ppn: str = Field(primary_key=True)
    dst_ppn: str = Field(primary_key=True)

    __table_args__ = (PrimaryKeyConstraint("src_ppn", "dst_ppn"),)


class test2(SQLModel, table=True):
    src_ppn: str = Field(primary_key=True)
    dst_ppn: str = Field(primary_key=True)


engine = create_engine("sqlite:///", echo=True)


SQLModel.metadata.create_all(engine)

Output (as you can see there is no difference):

CREATE TABLE test (
        src_ppn VARCHAR NOT NULL, 
        dst_ppn VARCHAR NOT NULL, 
        PRIMARY KEY (src_ppn, dst_ppn)
)

CREATE TABLE test2 (
        src_ppn VARCHAR NOT NULL, 
        dst_ppn VARCHAR NOT NULL, 
        PRIMARY KEY (src_ppn, dst_ppn)
)