eschutho opened a new pull request, #35540:
URL: https://github.com/apache/superset/pull/35540
### SUMMARY
Refactors the `select_star` method across all database engine specs to use
`dialect: Dialect` instead of `engine: Engine` as a parameter. This
optimization prevents unnecessary SSH tunnel connections from being created
when only the database dialect is needed for SQL generation.
**Problem**: The previous implementation used `get_sqla_engine()` which
establishes a full database connection (including SSH tunnels when configured),
but the `select_star` method only needs the dialect to generate SQL statements.
**Solution**:
- Changed `select_star` method signature from `engine: Engine` to `dialect:
Dialect` in `BaseEngineSpec` and all subclasses (BigQuery, Hive, Presto)
- Updated `Database.select_star()` to call lightweight `get_dialect()`
instead of `get_sqla_engine()`
- Removed unused `Engine` imports from Hive and Presto engine specs
- Updated all related unit tests to pass `dialect` instead of `engine`
**Impact**: This reduces unnecessary connection overhead, particularly for
databases configured with SSH tunnels, improving performance when generating
SELECT statements for table previews.
### BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF
N/A - Backend refactoring only, no UI changes
### TESTING INSTRUCTIONS
1. Run the updated unit tests:
```bash
pytest tests/unit_tests/db_engine_specs/ -k select_star -v
```
All 5 tests should pass (base, bigquery, hive, postgres, presto)
2. Verify type checking passes:
```bash
pre-commit run mypy
```
3. (Optional) Test with a database configured with SSH tunnel:
- Configure a database connection with SSH tunnel
- View a table in SQL Lab
- Verify table preview loads correctly without creating extra SSH
connections
### ADDITIONAL INFORMATION
- [ ] 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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