add sql_nullable param

README.md

@@ -657,7 +657,8 @@ The following keyword arguments are supported on all field types.
 
 All fields are required unless one of the following is set:
 
-* `nullable` - Creates a nullable column. Sets the default to `None`.
+* `nullable` - Creates a nullable column. Sets the default to `False`. Read the fields common parameters for details.
+* `sql_nullable` - Used to set different setting for pydantic and the database. Sets the default to `nullable` value. Read the fields common parameters for details.
 * `default` - Set a default value for the field. **Not available for relation fields**
 * `server_default` - Set a default value for the field on server side (like sqlalchemy's `func.now()`). **Not available for relation fields**
 * `primary key` with `autoincrement` - When a column is set to primary key and autoincrement is set on this column.

docs/fields/common-parameters.md

@@ -22,18 +22,41 @@ 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. 
+`nullable`: `bool` = `False` -> defaults to False for all fields except relation fields.
+
+Automatically changed to True if user provide one of the following:
+
+* `default` value or function is provided
+* `server_default` value or function is provided
+* `autoincrement` is set on `Integer` `primary_key` field
+* **[DEPRECATED]**`pydantic_only=True` is set 
 
 Specifies if field is optional or required, used both with sql and pydantic.
 
+By default, used for both `pydantic` and `sqlalchemy` as those are the most common settings:
+
+* `nullable=False` - means database column is not null and field is required in pydantic
+* `nullable=True` - means database column is null and field is optional in pydantic
+
+If you want to set different setting for pydantic and the database see `sql_nullable` below.
+
 !!!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][queries] and [relations][relations] sections. 
+## sql_nullable
+
+`sql_nullable`: `bool` = `nullable` -> defaults to the value of nullable (described above). 
+
+Specifies if field is not null or allows nulls in the database only. 
+
+Use this setting in combination with `nullable` only if you want to set different options on pydantic model and in the database. 
+
+A sample usage might be i.e. making field not null in the database, but allow this field to be nullable in pydantic (i.e. with `server_default` value).
+That will prevent the updates of the field to null (as with `server_default` set you cannot insert null values already as the default value would be used)
+
 
 
 ## default

docs/index.md

@@ -660,7 +660,8 @@ The following keyword arguments are supported on all field types.
 
 All fields are required unless one of the following is set:
 
-  * `nullable` - Creates a nullable column. Sets the default to `None`.
+  * `nullable` - Creates a nullable column. Sets the default to `False`. Read the fields common parameters for details.
+  * `sql_nullable` - Used to set different setting for pydantic and the database. Sets the default to `nullable` value. Read the fields common parameters for details.
   * `default` - Set a default value for the field. **Not available for relation fields**
   * `server_default` - Set a default value for the field on server side (like sqlalchemy's `func.now()`). **Not available for relation fields**
   * `primary key` with `autoincrement` - When a column is set to primary key and autoincrement is set on this column. 

ormar/fields/base.py

@@ -43,6 +43,7 @@ class BaseField(FieldInfo):
         self.primary_key: bool = kwargs.pop("primary_key", False)
         self.autoincrement: bool = kwargs.pop("autoincrement", False)
         self.nullable: bool = kwargs.pop("nullable", False)
+        self.sql_nullable: bool = kwargs.pop("sql_nullable", False)
         self.index: bool = kwargs.pop("index", False)
         self.unique: bool = kwargs.pop("unique", False)
         self.pydantic_only: bool = kwargs.pop("pydantic_only", False)
@@ -265,7 +266,7 @@ class BaseField(FieldInfo):
                 self.column_type,
                 *self.construct_constraints(),
                 primary_key=self.primary_key,
-                nullable=self.nullable and not self.primary_key,
+                nullable=self.sql_nullable,
                 index=self.index,
                 unique=self.unique,
                 default=self.ormar_default,

ormar/fields/foreign_key.py

@@ -234,6 +234,9 @@ def ForeignKey(  # noqa CFQ002
     skip_reverse = kwargs.pop("skip_reverse", False)
     skip_field = kwargs.pop("skip_field", False)
 
+    sql_nullable = kwargs.pop("sql_nullable", None)
+    sql_nullable = nullable if sql_nullable is None else sql_nullable
+
     validate_not_allowed_fields(kwargs)
 
     if to.__class__ == ForwardRef:
@@ -255,6 +258,7 @@ def ForeignKey(  # noqa CFQ002
         alias=name,
         name=kwargs.pop("real_name", None),
         nullable=nullable,
+        sql_nullable=sql_nullable,
         constraints=constraints,
         unique=unique,
         column_type=column_type,

ormar/fields/model_fields.py

@@ -75,6 +75,7 @@ class ModelFieldFactory:
         default = kwargs.pop("default", None)
         server_default = kwargs.pop("server_default", None)
         nullable = kwargs.pop("nullable", None)
+        sql_nullable = kwargs.pop("sql_nullable", None)
         pydantic_only = kwargs.pop("pydantic_only", False)
 
         primary_key = kwargs.pop("primary_key", False)
@@ -86,6 +87,13 @@ class ModelFieldFactory:
 
         overwrite_pydantic_type = kwargs.pop("overwrite_pydantic_type", None)
 
+        nullable = is_field_nullable(
+            nullable, default, server_default, pydantic_only
+        ) or is_auto_primary_key(primary_key, autoincrement)
+        sql_nullable = (
+            nullable if sql_nullable is None else (sql_nullable and not primary_key)
+        )
+
         namespace = dict(
             __type__=cls._type,
             __pydantic_type__=overwrite_pydantic_type
@@ -97,8 +105,8 @@ class ModelFieldFactory:
             primary_key=primary_key,
             default=default,
             server_default=server_default,
-            nullable=is_field_nullable(nullable, default, server_default, pydantic_only)
-            or is_auto_primary_key(primary_key, autoincrement),
+            nullable=nullable,
+            sql_nullable=sql_nullable,
             index=kwargs.pop("index", False),
             unique=kwargs.pop("unique", False),
             pydantic_only=pydantic_only,

tests/test_model_definition/test_overwriting_sql_nullable.py

@@ -0,0 +1,62 @@
+import sqlite3
+from typing import Optional
+
+import asyncpg
+import databases
+import pymysql
+import sqlalchemy
+from sqlalchemy import create_engine, text
+
+import ormar
+import pytest
+
+from tests.settings import DATABASE_URL
+
+db = databases.Database(DATABASE_URL, force_rollback=True)
+metadata = sqlalchemy.MetaData()
+
+
+class BaseMeta(ormar.ModelMeta):
+    metadata = metadata
+    database = db
+
+
+class PrimaryModel(ormar.Model):
+    class Meta(BaseMeta):
+        tablename = "primary_models"
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=255, index=True)
+    some_text: Optional[str] = ormar.Text(nullable=True, sql_nullable=False)
+    some_other_text: Optional[str] = ormar.Text(
+        nullable=True, sql_nullable=False, server_default=text("''")
+    )
+
+
+@pytest.fixture(autouse=True, scope="module")
+def create_test_database():
+    engine = create_engine(DATABASE_URL)
+    metadata.create_all(engine)
+    yield
+    metadata.drop_all(engine)
+
+
+@pytest.mark.asyncio
+async def test_create_models():
+    async with db:
+        primary = await PrimaryModel(
+            name="Foo", some_text="Bar", some_other_text="Baz"
+        ).save()
+        assert primary.id == 1
+
+        primary2 = await PrimaryModel(name="Foo2", some_text="Bar2").save()
+        assert primary2.id == 2
+
+        with pytest.raises(
+            (
+                sqlite3.IntegrityError,
+                pymysql.IntegrityError,
+                asyncpg.exceptions.NotNullViolationError,
+            )
+        ):
+            await PrimaryModel(name="Foo3").save()