fix(alembic): make migration scripts idempotent to resolve upgrade errors

- Checked column existence dynamically in `20260330_refactor_user_system_phase2.py` before querying and altering columns (`username`, `email`, etc.) that might have already been moved/dropped.
- Updated `add_participants.py` backfill logic to conditionally select `username` from the `identities` table via a LEFT JOIN, preventing missing column errors on the `users` table.
- Added conditional checks in `d9cbd43b62e5_add_llm_request_timeout.py` to prevent `DuplicateColumnError` when adding the `request_timeout` column.
- Added a pre-condition check in `user_refactor.py` to ensure the `email` column still exists on the `users` table before attempting to create the `ix_users_tenant_email_unique` index.

Author: jayeeliu

backend/alembic/versions/20260330_refactor_user_system_phase2.py

@@ -61,9 +61,16 @@ def upgrade() -> None:
         op.create_foreign_key('fk_users_identity_id', 'users', 'identities', ['identity_id'], ['id'])
 
     # 5. Data migration (idempotent)
-    # Only migrate users that don't have an identity_id yet
-    result = conn.execute(sa.text("""
-        SELECT id, email, primary_mobile, username, password_hash, email_verified, is_active, role 
+    user_columns = [c['name'] for c in inspector.get_columns('users')]
+    
+    email_col = 'email' if 'email' in user_columns else 'NULL as email'
+    phone_col = 'primary_mobile' if 'primary_mobile' in user_columns else 'NULL as primary_mobile'
+    username_col = 'username' if 'username' in user_columns else 'NULL as username'
+    pwd_col = 'password_hash' if 'password_hash' in user_columns else 'NULL as password_hash'
+    ev_col = 'email_verified' if 'email_verified' in user_columns else 'NULL as email_verified'
+    
+    result = conn.execute(sa.text(f"""
+        SELECT id, {email_col}, {phone_col}, {username_col}, {pwd_col}, {ev_col}, is_active, role 
         FROM users 
         WHERE identity_id IS NULL
     """))
@@ -120,8 +127,10 @@ def upgrade() -> None:
             })
 
     # 6. Cleanup: Make username/email nullable and DROP redundant columns
-    op.alter_column('users', 'username', existing_type=sa.String(length=100), nullable=True)
-    op.alter_column('users', 'email', existing_type=sa.String(length=255), nullable=True)
+    if 'username' in user_columns:
+        op.alter_column('users', 'username', existing_type=sa.String(length=100), nullable=True)
+    if 'email' in user_columns:
+        op.alter_column('users', 'email', existing_type=sa.String(length=255), nullable=True)
 
     # Physically drop redundant columns
     op.execute("ALTER TABLE users DROP COLUMN IF EXISTS username")

backend/alembic/versions/add_participants.py

@@ -32,8 +32,9 @@ def upgrade() -> None:
     # 2. Backfill: create Participant for every existing User
     conn.execute(sa.text("""
         INSERT INTO participants (id, type, ref_id, display_name, avatar_url)
-        SELECT gen_random_uuid(), 'user', id, COALESCE(display_name, username), avatar_url
-        FROM users
+        SELECT gen_random_uuid(), 'user', u.id, COALESCE(u.display_name, i.username, 'User'), u.avatar_url
+        FROM users u
+        LEFT JOIN identities i ON u.identity_id = i.id
         ON CONFLICT DO NOTHING
     """))
 

backend/alembic/versions/d9cbd43b62e5_add_llm_request_timeout.py

@@ -19,7 +19,11 @@
 
 def upgrade() -> None:
     # ### commands auto generated by Alembic - please adjust! ###
-    op.add_column('llm_models', sa.Column('request_timeout', sa.Integer(), nullable=True))
+    conn = op.get_bind()
+    inspector = sa.inspect(conn)
+    columns = [c['name'] for c in inspector.get_columns('llm_models')]
+    if 'request_timeout' not in columns:
+        op.add_column('llm_models', sa.Column('request_timeout', sa.Integer(), nullable=True))
     # ### end Alembic commands ###
 
 

backend/alembic/versions/user_refactor.py

@@ -144,10 +144,15 @@ def upgrade() -> None:
     op.execute("""
         DO $$
         BEGIN
-            IF NOT EXISTS (
-                SELECT 1 FROM pg_indexes WHERE indexname = 'ix_users_tenant_email_unique'
+            IF EXISTS (
+                SELECT 1 FROM information_schema.columns
+                WHERE table_name = 'users' AND column_name = 'email'
             ) THEN
-                CREATE UNIQUE INDEX ix_users_tenant_email_unique ON users(tenant_id, email) WHERE email IS NOT NULL;
+                IF NOT EXISTS (
+                    SELECT 1 FROM pg_indexes WHERE indexname = 'ix_users_tenant_email_unique'
+                ) THEN
+                    CREATE UNIQUE INDEX ix_users_tenant_email_unique ON users(tenant_id, email) WHERE email IS NOT NULL;
+                END IF;
             END IF;
         END $$
     """)