some new models

backend/app/models.py

@@ -1,6 +1,8 @@
 from datetime import datetime
 from typing import Optional
 from sqlmodel import Field, SQLModel, UUID, TIMESTAMP, text, Column
+from sqlalchemy.schema import DDL
+from sqlalchemy import event
 
 
 class UUIDType(UUID):
@@ -36,3 +38,35 @@ class GerryDBTableBase(TimeStampMixin, SQLModel):
 class GerryDBTable(GerryDBTableBase, table=True):
     uuid: str = Field(sa_column=Column(UUIDType, unique=True))
     name: str = Field(nullable=False, unique=True)
+
+
+class Document(TimeStampMixin, SQLModel):
+    document_id: str = Field(sa_column=Column(UUIDType), unique=True)
+
+
+class AssignmentsMixin(SQLModel):
+    # mixin used for defining parent table + each partition on the fly
+    document_id: str = Field(foreign_key="document.document_id")
+    geo_id: str
+    zone: int
+
+
+class Assignments(AssignmentsMixin, table=True):
+    # this is the empty parent table; not a partition itself
+
+    __table_args__ = {"postgres_partition_by": "document_id"}
+
+
+# one time, create the trigger that creates new assignments partitions
+create_partition_trigger = DDL(
+    """
+        CREATE TRIGGER create_assignment_partition AFTER INSERT ON document
+        
+        BEGIN
+            CREATE TABLE assignments_{document_id} PARTITION OF assignments
+        VALUES IN (new.document_id)
+        END 
+        """
+)
+# do it when the document table is created
+event.listen(Document.__table, "after_create", create_partition_trigger)