Fix migration constraint naming double-prefix and NULL in mixed metadata lists

- Use fully-rendered constraint names in migration 0003 to avoid the
  naming convention doubling the ck_ prefix on batch operations.
- Add table_args to downgrade so SQLite batch mode can find the CHECK
  constraint (not exposed by SQLite reflection).
- Fix model CheckConstraint name to use bare 'has_value' (convention
  auto-prefixes).
- Skip None items when converting metadata lists to rows, preventing
  all-NULL rows that violate the has_value check constraint.

Amp-Thread-ID: https://ampcode.com/threads/T-019cef87-94f9-7172-a6af-c6282290ce4f
Co-authored-by: Amp <amp@ampcode.com>

alembic_db/versions/0003_add_metadata_job_id.py

@@ -53,9 +53,7 @@ def upgrade() -> None:
         "DELETE FROM asset_reference_meta"
         " WHERE val_str IS NULL AND val_num IS NULL AND val_bool IS NULL AND val_json IS NULL"
     )
-    with op.batch_alter_table(
-        "asset_reference_meta", naming_convention=NAMING_CONVENTION
-    ) as batch_op:
+    with op.batch_alter_table("asset_reference_meta") as batch_op:
         batch_op.create_check_constraint(
             "ck_asset_reference_meta_has_value",
             "val_str IS NOT NULL OR val_num IS NOT NULL OR val_bool IS NOT NULL OR val_json IS NOT NULL",
@@ -63,8 +61,18 @@ def upgrade() -> None:
 
 
 def downgrade() -> None:
+    # SQLite doesn't reflect CHECK constraints, so we must declare it
+    # explicitly via table_args for the batch recreate to find it.
+    # Use the fully-rendered constraint name to avoid the naming convention
+    # doubling the prefix.
     with op.batch_alter_table(
-        "asset_reference_meta", naming_convention=NAMING_CONVENTION
+        "asset_reference_meta",
+        table_args=[
+            sa.CheckConstraint(
+                "val_str IS NOT NULL OR val_num IS NOT NULL OR val_bool IS NOT NULL OR val_json IS NOT NULL",
+                name="ck_asset_reference_meta_has_value",
+            ),
+        ],
     ) as batch_op:
         batch_op.drop_constraint(
             "ck_asset_reference_meta_has_value", type_="check"

app/assets/database/models.py

@@ -193,7 +193,7 @@ class AssetReferenceMeta(Base):
         Index("ix_asset_reference_meta_key_val_bool", "key", "val_bool"),
         CheckConstraint(
             "val_str IS NOT NULL OR val_num IS NOT NULL OR val_bool IS NOT NULL OR val_json IS NOT NULL",
-            name="ck_asset_reference_meta_has_value",
+            name="has_value",
         ),
     )
 

app/assets/database/queries/asset_reference.py

@@ -66,8 +66,8 @@ def convert_metadata_to_rows(key: str, value) -> list[dict]:
 
     if isinstance(value, list):
         if all(_check_is_scalar(x) for x in value):
-            return [_scalar_to_row(key, i, x) for i, x in enumerate(value)]
-        return [{"key": key, "ordinal": i, "val_json": x} for i, x in enumerate(value)]
+            return [_scalar_to_row(key, i, x) for i, x in enumerate(value) if x is not None]
+        return [{"key": key, "ordinal": i, "val_json": x} for i, x in enumerate(value) if x is not None]
 
     return [{"key": key, "ordinal": 0, "val_json": value}]