3.4 KiB
Common Parameters
All Field types have a set of common parameters.
primary_key
primary_key: bool = False -> by default False.
Sets the primary key column on a table, foreign keys always refer to the pk of the Model.
Used in sql only.
autoincrement
autoincrement: bool = primary_key and type == int -> defaults to True if column is a primary key and of type Integer, otherwise False.
Can be only used with int/bigint fields.
If a field has autoincrement it becomes optional.
Used both in sql and pydantic (changes pk field to optional for autoincrement).
nullable
nullable: bool = not primary_key -> defaults to False for primary key column, and True for all other.
Specifies if field is optional or required, used both with sql and pydantic.
!!!note
By default all ForeignKeys are also nullable, meaning the related Model is not required.
If you change the `ForeignKey` column to `nullable=False`, it becomes required.
!!!info If you want to know more about how you can preload related models during queries and how the relations work read the queries and relations sections.
default
default: Any = None -> defaults to None.
A default value used if no other value is passed.
In sql invoked on an insert, used during pydantic model definition.
If the field has a default value it becomes optional.
You can pass a static value or a Callable (function etc.)
Used both in sql and pydantic.
server default
server_default: Any = None -> defaults to None.
A default value used if no other value is passed.
In sql invoked on the server side so you can pass i.e. sql function (like now() or query/value wrapped in sqlalchemy text() clause).
If the field has a server_default value it becomes optional.
You can pass a static value or a Callable (function etc.)
Used in sql only.
Sample usage:
--8<-- "../docs_src/fields/docs004.py"
!!!warning
server_default accepts str, sqlalchemy.sql.elements.ClauseElement or sqlalchemy.sql.elements.TextClause
so if you want to set i.e. Integer value you need to wrap it in sqlalchemy.text() function like above
!!!tip
You can pass also valid sql (dialect specific) wrapped in sqlalchemy.text()
For example `func.now()` above could be exchanged for `text('(CURRENT_TIMESTAMP)')` for sqlite backend
!!!info
server_default is passed straight to sqlalchemy table definition so you can read more in server default sqlalchemy documentation
index
index: bool = False -> by default False,
Sets the index on a table's column.
Used in sql only.
unique
unique: bool = False
Sets the unique constraint on a table's column.
Used in sql only.
pydantic_only
pydantic_only: bool = False
Prevents creation of a sql column for given field.
Used for data related to given model but not to be stored in the database.
Used in pydantic only.
choices
choices: Sequence = []
A set of choices allowed to be used for given field.
Used for data validation on pydantic side.
Prevents insertion of value not present in the choices list.
Used in pydantic only.