fix: use clock_timestamp() instead of now() for Mixin to ensure unique values (#138)

docs/module/models.md

@@ -18,7 +18,7 @@ class Article(Base, UUIDMixin, TimestampMixin):
     content: Mapped[str]
 ```
 
-All timestamp columns are timezone-aware (`TIMESTAMPTZ`). All defaults are server-side, so they are also applied when inserting rows via raw SQL outside the ORM.
+All timestamp columns are timezone-aware (`TIMESTAMPTZ`). All defaults are server-side (`clock_timestamp()`), so they are also applied when inserting rows via raw SQL outside the ORM.
 
 ## Mixins
 
@@ -42,7 +42,7 @@ print(user.id)  # UUID('...')
 
 ### [`CreatedAtMixin`](../reference/models.md#fastapi_toolsets.models.CreatedAtMixin)
 
-Adds a `created_at: datetime` column set to `NOW()` on insert. The column has no `onupdate` hook — it is intentionally immutable after the row is created.
+Adds a `created_at: datetime` column set to `clock_timestamp()` on insert. The column has no `onupdate` hook — it is intentionally immutable after the row is created.
 
 ```python
 from fastapi_toolsets.models import UUIDMixin, CreatedAtMixin
@@ -55,7 +55,7 @@ class Order(Base, UUIDMixin, CreatedAtMixin):
 
 ### [`UpdatedAtMixin`](../reference/models.md#fastapi_toolsets.models.UpdatedAtMixin)
 
-Adds an `updated_at: datetime` column set to `NOW()` on insert and automatically updated to `NOW()` on every ORM-level update (via SQLAlchemy's `onupdate` hook).
+Adds an `updated_at: datetime` column set to `clock_timestamp()` on insert and automatically updated to `clock_timestamp()` on every ORM-level update (via SQLAlchemy's `onupdate` hook).
 
 ```python
 from fastapi_toolsets.models import UUIDMixin, UpdatedAtMixin

docs_src/examples/pagination_search/models.py

@@ -1,9 +1,10 @@
-import datetime
 import uuid
 
-from sqlalchemy import Boolean, DateTime, ForeignKey, String, Text, func
+from sqlalchemy import Boolean, ForeignKey, String, Text
 from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
 
+from fastapi_toolsets.models import CreatedAtMixin
+
 
 class Base(DeclarativeBase):
     pass
@@ -18,13 +19,10 @@ class Category(Base):
     articles: Mapped[list["Article"]] = relationship(back_populates="category")
 
 
-class Article(Base):
+class Article(Base, CreatedAtMixin):
     __tablename__ = "articles"
 
     id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
-    created_at: Mapped[datetime.datetime] = mapped_column(
-        DateTime(timezone=True), server_default=func.now()
-    )
     title: Mapped[str] = mapped_column(String(256))
     body: Mapped[str] = mapped_column(Text)
     status: Mapped[str] = mapped_column(String(32))

src/fastapi_toolsets/models.py

@@ -3,7 +3,7 @@
 import uuid
 from datetime import datetime
 
-from sqlalchemy import DateTime, Uuid, func, text
+from sqlalchemy import DateTime, Uuid, text
 from sqlalchemy.orm import Mapped, mapped_column
 
 __all__ = [
@@ -29,7 +29,7 @@ class CreatedAtMixin:
 
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),
-        server_default=func.now(),
+        server_default=text("clock_timestamp()"),
     )
 
 
@@ -38,8 +38,8 @@ class UpdatedAtMixin:
 
     updated_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),
-        server_default=func.now(),
-        onupdate=func.now(),
+        server_default=text("clock_timestamp()"),
+        onupdate=text("clock_timestamp()"),
     )