massucattoj opened a new pull request, #42203:
URL: https://github.com/apache/superset/pull/42203
### SUMMARY
Columns of MySQL virtual datasets (created from SQL Lab queries) showed a
"?" type icon in the chart panel instead of ABC/#, which also hid
type-dependent controls such as X-Axis Sort By.
Physical datasets get column types from the SQLAlchemy inspector as DDL
names (`VARCHAR(100)`, `DECIMAL(15,2)`), which match
`MySQLEngineSpec.column_type_mappings`. Virtual dataset columns instead get
their type from the driver's cursor description via `get_datatype`, which
returns the raw wire-protocol `FIELD_TYPE` constant names (`VAR_STRING` for
VARCHAR, `NEWDECIMAL` for DECIMAL, `TINY` for TINYINT, `BLOB` for TEXT, and so
on). None of those names matched any mapping regex, so `type_generic` resolved
to `None`.
This PR adds mappings for the 8 wire-protocol names that had no match:
`VAR_STRING`, `NEWDECIMAL`, `TINY`, `SHORT`, `BLOB`, `YEAR`, `ENUM` and `SET`.
Regexes are anchored so they don't collide with existing DDL patterns (`^tiny$`
vs `^tinytext`), and `^enum\b`/`^set\b` also cover the DDL forms
(`ENUM('a','b')`), which were equally unresolved.
Fixing the type resolution exposed a second, latent bug: MySQL registers a
`column_type_mutators` entry that converts DECIMAL string values to Python
`Decimal`, keyed on the resolved column type. It had never fired because
`NEWDECIMAL` never resolved. Once it did, `BaseEngineSpec.fetch_data` crashed
with `TypeError: 'tuple' object does not support item assignment`, because the
mutation loop assigns rows back into the `fetchall()` result and mysqlclient
returns a tuple of rows (psycopg2 returns a list, which is why the same code
works for Postgres). Fixed by copying the result into a list before mutating.
### BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF
<img width="1581" height="784" alt="Screenshot 2026-07-18 at 12 59 02"
src="https://github.com/user-attachments/assets/63ac1ace-a257-4bf4-92eb-9a1948707fd4";
/>
After:
<img width="1497" height="837" alt="Screenshot 2026-07-18 at 12 59 27"
src="https://github.com/user-attachments/assets/c31907a7-2392-43bd-a2c8-c2a4e77ed06c";
/>
### TESTING INSTRUCTIONS
1. Start a MySQL instance and create a table exercising the affected types:
```sql
CREATE TABLE sample_data (
id INT AUTO_INCREMENT PRIMARY KEY,
label VARCHAR(100),
amount DECIMAL(15, 2)
);
INSERT INTO sample_data (label, amount) VALUES ('Ships', 10.50),
('Planes', 22.30);
2. Connect the MySQL database to Superset.
3. In SQL Lab, run SELECT * FROM sample_data and use "Save or Overwrite
Dataset" to save it as a new (virtual) dataset.
4. Create a chart from that dataset.
5. Verify label shows the string indicator, amount and id show the numeric
indicator, and the chart renders data instead of a type error.
### ADDITIONAL INFORMATION
<!--- Check any relevant boxes with "x" -->
<!--- HINT: Include "Fixes #nnn" if you are fixing an existing issue -->
- [ ] Has associated issue:
- [ ] Required feature flags:
- [ ] Changes UI
- [ ] Includes DB Migration (follow approval process in
[SIP-59](https://github.com/apache/superset/issues/13351))
- [ ] Migration is atomic, supports rollback & is backwards-compatible
- [ ] Confirm DB migration upgrade and downgrade tested
- [ ] Runtime estimates and downtime expectations provided
- [ ] Introduces new feature or API
- [ ] Removes existing feature or API
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