diff --git a/backend/alembic/alembic.ini b/backend/alembic/alembic.ini
index 37b1a50..160fab4 100644
--- a/backend/alembic/alembic.ini
+++ b/backend/alembic/alembic.ini
@@ -1,6 +1,12 @@
 [alembic]
 script_location = alembic
 sqlalchemy.url = postgresql://scilit:scilit_dev@localhost:5432/scilit
+# Commit each migration in its own transaction (default: whole upgrade in one).
+# Rewrite-heavy migrations (JSON->JSONB / ALTER COLUMN TYPE DATE) on the
+# 1.23M-row prod table peak at huge disk usage; one shared txn accumulates
+# them -> disk-full (2026-08-10 batch 1 incident root cause).
+# Independent commits release space early.
+transaction_per_migration = true
 
 [loggers]
 keys = root,sqlalchemy,alembic
diff --git a/backend/alembic/versions/1421ea169bb6_change_5_date_fields_to_date.py b/backend/alembic/versions/1421ea169bb6_change_5_date_fields_to_date.py
index a58c009..a6db69e 100644
--- a/backend/alembic/versions/1421ea169bb6_change_5_date_fields_to_date.py
+++ b/backend/alembic/versions/1421ea169bb6_change_5_date_fields_to_date.py
@@ -21,19 +21,19 @@ DATE_FIELDS = ["pubmed_revised", "date_completed", "meshed_date", "create_date",
 
 
 def upgrade() -> None:
-    for col in DATE_FIELDS:
-        op.alter_column("global_literature", col,
-            existing_type=postgresql.TIMESTAMP(timezone=True),
-            type_=sa.Date(),
-            existing_nullable=True,
-            postgresql_using=f"{col}::date",
-        )
+    # 合并为单条 ALTER：5 列一次全表重写。
+    # 原实现循环逐个 ALTER = 5 次整表重写，同一事务内空间峰值叠加，
+    # 生产 123 万行表（~9.8GB）会爆盘（2026-08-10 批次 1 事故根因）。
+    _cols = ", ".join(
+        f'ALTER COLUMN "{col}" TYPE DATE USING "{col}"::date'
+        for col in DATE_FIELDS
+    )
+    op.execute(f"ALTER TABLE global_literature {_cols}")
 
 
 def downgrade() -> None:
-    for col in reversed(DATE_FIELDS):
-        op.alter_column("global_literature", col,
-            existing_type=sa.Date(),
-            type_=postgresql.TIMESTAMP(timezone=True),
-            existing_nullable=True,
-        )
+    _cols = ", ".join(
+        f'ALTER COLUMN "{col}" TYPE TIMESTAMP WITH TIME ZONE'
+        for col in reversed(DATE_FIELDS)
+    )
+    op.execute(f"ALTER TABLE global_literature {_cols}")