fix(migrations): make DDL idempotent on partial-failure reruns

Migration 0084 could fail on startup with "Duplicate key name
'idx_roms_name_fs_name_fulltext'" when a prior run created the FULLTEXT
index but failed at a later step before Alembic recorded the revision.
On rerun, CREATE FULLTEXT INDEX (which has no portable IF NOT EXISTS on
MySQL/MariaDB) crashed re-creating the existing index.

Guard the raw DDL so re-running a partially-applied migration is safe:

- 0084: check existing indexes before creating/dropping the FULLTEXT index
- 0014: check existing columns before the raw ALTER TABLE ADD COLUMN id
- 0033: use checkfirst=True on the Postgres enum create/drop

Generated-By: PostHog Code
Task-Id: 87d70ab6-f915-48c0-afa7-55064c97d1a5

Author: gantoine

backend/alembic/versions/0014_asset_files.py

@@ -168,13 +168,18 @@ def upgrade() -> None:
         batch_op.drop_constraint(constraint_name=pk_constraint_name, type_="primary")
         batch_op.drop_column("n_roms", if_exists=True)
 
-    # Switch to new id column as platform primary key
-    if is_postgresql(connection):
-        op.execute("ALTER TABLE platforms ADD COLUMN id SERIAL PRIMARY KEY")
-    else:
-        op.execute(
-            "ALTER TABLE platforms ADD COLUMN id INTEGER(11) NOT NULL AUTO_INCREMENT PRIMARY KEY"
-        )
+    # Switch to new id column as platform primary key. Raw DDL has no portable
+    # "IF NOT EXISTS", so guard it to stay idempotent on a partial-failure rerun.
+    platform_columns = {
+        column["name"] for column in sa.inspect(connection).get_columns("platforms")
+    }
+    if "id" not in platform_columns:
+        if is_postgresql(connection):
+            op.execute("ALTER TABLE platforms ADD COLUMN id SERIAL PRIMARY KEY")
+        else:
+            op.execute(
+                "ALTER TABLE platforms ADD COLUMN id INTEGER(11) NOT NULL AUTO_INCREMENT PRIMARY KEY"
+            )
 
     # Add new columns to roms table
     with op.batch_alter_table("roms", schema=None) as batch_op:

backend/alembic/versions/0033_rom_file_and_hashes.py

@@ -37,7 +37,7 @@ def upgrade() -> None:
             name="romfilecategory",
             create_type=False,
         )
-        rom_file_category_enum.create(connection, checkfirst=False)
+        rom_file_category_enum.create(connection, checkfirst=True)
     else:
         rom_file_category_enum = sa.Enum(
             "GAME",
@@ -263,4 +263,4 @@ def downgrade() -> None:
     op.drop_table("rom_files", if_exists=True)
 
     if is_postgresql(connection):
-        ENUM(name="romfilecategory").drop(connection, checkfirst=False)
+        ENUM(name="romfilecategory").drop(connection, checkfirst=True)

backend/alembic/versions/0084_add_roms_search_index.py

@@ -47,12 +47,18 @@ def upgrade() -> None:
 
     # 1. DB-specific search indexes on roms.name and roms.fs_name.
     if is_mysql(bind) or is_mariadb(bind):
-        op.execute(
-            sa.text(
-                f"CREATE FULLTEXT INDEX {FULLTEXT_INDEX_NAME} "
-                "ON roms (name, fs_name)"
+        # MySQL/MariaDB have no portable "IF NOT EXISTS" for FULLTEXT indexes, so
+        # guard the create to stay idempotent if a prior run partially applied.
+        existing_indexes = {
+            index["name"] for index in sa.inspect(bind).get_indexes("roms")
+        }
+        if FULLTEXT_INDEX_NAME not in existing_indexes:
+            op.execute(
+                sa.text(
+                    f"CREATE FULLTEXT INDEX {FULLTEXT_INDEX_NAME} "
+                    "ON roms (name, fs_name)"
+                )
             )
-        )
     elif is_postgresql(bind):
         # pg_trgm is a trusted extension since PostgreSQL 13, so a non-superuser
         # with CREATE on the database can install it.
@@ -130,7 +136,12 @@ def downgrade() -> None:
 
     # 1. DB-specific search indexes.
     if is_mysql(bind) or is_mariadb(bind):
-        op.execute(sa.text(f"DROP INDEX {FULLTEXT_INDEX_NAME} ON roms"))
+        # MySQL has no portable "IF EXISTS" for DROP INDEX, so guard the drop.
+        existing_indexes = {
+            index["name"] for index in sa.inspect(bind).get_indexes("roms")
+        }
+        if FULLTEXT_INDEX_NAME in existing_indexes:
+            op.execute(sa.text(f"DROP INDEX {FULLTEXT_INDEX_NAME} ON roms"))
     elif is_postgresql(bind):
         # Leave the pg_trgm extension in place; other objects may depend on it.
         op.execute(sa.text(f"DROP INDEX IF EXISTS {PG_FS_NAME_INDEX}"))