Improved workplan dependency management facilities

state-hub/migrations/versions/s6n7o8p9q0r1_workstream_planning_metadata.py

@@ -0,0 +1,96 @@
+"""add workstream planning metadata and typed dependency targets
+
+Revision ID: s6n7o8p9q0r1
+Revises: r5m6n7o8p9q0
+Create Date: 2026-05-04
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import UUID
+
+revision = "s6n7o8p9q0r1"
+down_revision = "r5m6n7o8p9q0"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("workstreams", sa.Column("planning_priority", sa.String(length=20), nullable=True))
+    op.add_column("workstreams", sa.Column("planning_order", sa.Integer(), nullable=True))
+    op.create_index("ix_workstreams_planning_priority", "workstreams", ["planning_priority"])
+    op.create_index("ix_workstreams_planning_order", "workstreams", ["planning_order"])
+
+    op.drop_constraint("uq_ws_dep_pair", "workstream_dependencies", type_="unique")
+    op.add_column("workstream_dependencies", sa.Column("to_task_id", UUID(as_uuid=True), nullable=True))
+    op.add_column(
+        "workstream_dependencies",
+        sa.Column("relationship_type", sa.String(length=40), nullable=False, server_default="blocks"),
+    )
+    op.alter_column(
+        "workstream_dependencies",
+        "to_workstream_id",
+        existing_type=UUID(as_uuid=True),
+        nullable=True,
+    )
+    op.create_foreign_key(
+        "fk_ws_dep_to_task_id",
+        "workstream_dependencies",
+        "tasks",
+        ["to_task_id"],
+        ["id"],
+        ondelete="CASCADE",
+    )
+    op.create_index("ix_workstream_dependencies_to_task_id", "workstream_dependencies", ["to_task_id"])
+    op.create_index(
+        "ix_workstream_dependencies_relationship_type",
+        "workstream_dependencies",
+        ["relationship_type"],
+    )
+    op.create_check_constraint(
+        "ck_ws_dep_exactly_one_target",
+        "workstream_dependencies",
+        "(to_workstream_id IS NOT NULL AND to_task_id IS NULL) "
+        "OR (to_workstream_id IS NULL AND to_task_id IS NOT NULL)",
+    )
+    op.create_index(
+        "uq_ws_dep_workstream_target",
+        "workstream_dependencies",
+        ["from_workstream_id", "to_workstream_id", "relationship_type"],
+        unique=True,
+        postgresql_where=sa.text("to_workstream_id IS NOT NULL"),
+    )
+    op.create_index(
+        "uq_ws_dep_task_target",
+        "workstream_dependencies",
+        ["from_workstream_id", "to_task_id", "relationship_type"],
+        unique=True,
+        postgresql_where=sa.text("to_task_id IS NOT NULL"),
+    )
+
+
+def downgrade() -> None:
+    op.drop_index("uq_ws_dep_task_target", table_name="workstream_dependencies")
+    op.drop_index("uq_ws_dep_workstream_target", table_name="workstream_dependencies")
+    op.drop_constraint("ck_ws_dep_exactly_one_target", "workstream_dependencies", type_="check")
+    op.drop_index("ix_workstream_dependencies_relationship_type", table_name="workstream_dependencies")
+    op.drop_index("ix_workstream_dependencies_to_task_id", table_name="workstream_dependencies")
+    op.drop_constraint("fk_ws_dep_to_task_id", "workstream_dependencies", type_="foreignkey")
+    op.alter_column(
+        "workstream_dependencies",
+        "to_workstream_id",
+        existing_type=UUID(as_uuid=True),
+        nullable=False,
+    )
+    op.drop_column("workstream_dependencies", "relationship_type")
+    op.drop_column("workstream_dependencies", "to_task_id")
+    op.create_unique_constraint(
+        "uq_ws_dep_pair",
+        "workstream_dependencies",
+        ["from_workstream_id", "to_workstream_id"],
+    )
+
+    op.drop_index("ix_workstreams_planning_order", table_name="workstreams")
+    op.drop_index("ix_workstreams_planning_priority", table_name="workstreams")
+    op.drop_column("workstreams", "planning_order")
+    op.drop_column("workstreams", "planning_priority")