Index Academics join table columns that back common queries (#497)

backend/entities/academics/section_entity.py

@@ -1,7 +1,7 @@
 """Definition of SQLAlchemy table-backed object mapping entity for Course Sections."""
 
 from typing import Self
-from sqlalchemy import Integer, String, ForeignKey
+from sqlalchemy import Integer, String, ForeignKey, Index
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 from ..entity_base import EntityBase
 from ..section_application_table import section_application_table
@@ -19,6 +19,22 @@ class SectionEntity(EntityBase):
     # Name for the course section table in the PostgreSQL database
     __tablename__ = "academics__section"
 
+    # Add indexes to the database for fast, common lookup queries
+    __table_args__ = (
+        Index(
+            "ix_academics__section__by_term",
+            "term_id",
+            "course_id",
+            unique=False,
+        ),
+        Index(
+            "ix_academics__section__by_course",
+            "course_id",
+            "term_id",
+            unique=False,
+        ),
+    )
+
     # Section properties (columns in the database table)
 
     # Unique ID for the section

backend/entities/academics/section_member_entity.py

@@ -1,12 +1,12 @@
 """Definition of SQLAlchemy table-backed object mapping entity for the user - section association table."""
 
 from typing import Self
-from sqlalchemy import ForeignKey, Integer
+from sqlalchemy import ForeignKey, Integer, Index
 from sqlalchemy import Enum as SQLAlchemyEnum
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
-from backend.entities.office_hours import user_created_tickets_table
-from backend.models.academics.section_member_details import SectionMemberDetails
+from ..office_hours import user_created_tickets_table
+from ...models.academics.section_member_details import SectionMemberDetails
 
 from ...models.roster_role import RosterRole
 from ...models.academics.section_member import SectionMember, SectionMemberDraft
@@ -37,6 +37,22 @@ class SectionMemberEntity(EntityBase):
     # Name for the user section table in the PostgreSQL database
     __tablename__ = "academics__user_section"
 
+    # Add indexes to the database for fast, common lookup queries
+    __table_args__ = (
+        Index(
+            "ix_academics__user_section__by_user",
+            "user_id",
+            "section_id",
+            unique=True,
+        ),
+        Index(
+            "ix_academics__user_section__by_section",
+            "section_id",
+            "member_role",
+            unique=False,
+        ),
+    )
+
     # User Section properties (columns in the database table)
 
     # Unique ID for a user's membership in an academic section
@@ -65,10 +81,6 @@ class SectionMemberEntity(EntityBase):
         back_populates="caller", cascade="all, delete"
     )
 
-    application_id: Mapped[int] = mapped_column(
-        ForeignKey("application.id"), nullable=True
-    )
-
     def to_flat_model(self) -> SectionMember:
         """
         Converts a `SectionEntity` object into a `SectionMember` model object

backend/migrations/versions/87dd1109e7b2_migration_for_academics_indexes.py

@@ -0,0 +1,76 @@
+"""Adds Indexes to Academics for common query patterns.
+
+Revision ID: 87dd1109e7b2
+Revises: eb379629af4f
+Create Date: 2024-06-08 07:17:36.113064
+
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "87dd1109e7b2"
+down_revision = "eb379629af4f"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Add indices to the academics__section and academics__user_section tables for common query patterns.
+    op.create_index(
+        "ix_academics__section__by_course",
+        "academics__section",
+        ["course_id", "term_id"],
+        unique=False,
+    )
+    op.create_index(
+        "ix_academics__section__by_term",
+        "academics__section",
+        ["term_id", "course_id"],
+        unique=False,
+    )
+
+    op.create_index(
+        "ix_academics__user_section__by_section",
+        "academics__user_section",
+        ["section_id", "member_role"],
+        unique=False,
+    )
+    op.create_index(
+        "ix_academics__user_section__by_user",
+        "academics__user_section",
+        ["user_id", "section_id"],
+        unique=True,
+    )
+
+    # Remove the foreign key to a TA application from UserSection. It will go somewhere else eventually.
+    op.drop_constraint(
+        "academics__user_section_application_id_fkey",
+        "academics__user_section",
+        type_="foreignkey",
+    )
+    op.drop_column("academics__user_section", "application_id")
+
+
+def downgrade() -> None:
+    op.add_column(
+        "academics__user_section",
+        sa.Column("application_id", sa.INTEGER(), autoincrement=False, nullable=True),
+    )
+    op.create_foreign_key(
+        "academics__user_section_application_id_fkey",
+        "academics__user_section",
+        "application",
+        ["application_id"],
+        ["id"],
+    )
+    op.drop_index(
+        "ix_academics__user_section__by_user", table_name="academics__user_section"
+    )
+    op.drop_index(
+        "ix_academics__user_section__by_section", table_name="academics__user_section"
+    )
+    op.drop_index("ix_academics__section__by_term", table_name="academics__section")
+    op.drop_index("ix_academics__section__by_course", table_name="academics__section")