justinpark commented on PR #39859:
URL: https://github.com/apache/superset/pull/39859#issuecomment-4425770485
I ran the attached the upgrade script and encountered the following error.
```
MySQLdb.OperationalError: (1832, "Cannot change column 'dashboard_id': used
in a foreign key constraint 'fk_dashboard_roles_dashboard_id_dashboards'")
```
I found the following fix with the help of Claude.
```
Apply the same MySQL FK-drop logic to the else branch:
else:
if conn.dialect.name == "mysql":
for fk in insp.get_foreign_keys(t.name):
if fk_name := fk.get("name"):
op.drop_constraint(fk_name, t.name, type_="foreignkey")
with op.batch_alter_table(t.name) as batch_op:
batch_op.drop_column("id")
batch_op.create_primary_key(f"pk_{t.name}", [t.fk1, t.fk2])
batch_op.alter_column(t.fk1, existing_type=sa.Integer,
nullable=False)
batch_op.alter_column(t.fk2, existing_type=sa.Integer,
nullable=False)
However, the cleaner fix is to unify the two branches since the MySQL
FK-drop logic is now identical — the only real difference between them is
whether a pre-existing UNIQUE constraint needs to be dropped, not how MySQL FKs
are handled:
# Drop FKs first on MySQL for ALL tables (not just
TABLES_WITH_PRE_EXISTING_UNIQUE)
if conn.dialect.name == "mysql":
for fk in insp.get_foreign_keys(t.name):
if fk_name := fk.get("name"):
op.drop_constraint(fk_name, t.name, type_="foreignkey")
if t.name in TABLES_WITH_PRE_EXISTING_UNIQUE:
with op.batch_alter_table(
t.name,
recreate="always",
copy_from=_build_pre_upgrade_table(insp, t),
) as batch_op:
...
else:
with op.batch_alter_table(t.name) as batch_op:
...
This separates the two concerns cleanly — MySQL FK handling applies to all
tables, and the recreate="always" path is only for tables with a pre-existing
UNIQUE.
The downgrade() function must mirror this in reverse order.
```
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