wsamyak-cars24 opened a new issue, #38189:
URL: https://github.com/apache/superset/issues/38189
### Bug description
### Superset version
6.0.0
### Additional environment info
- **Database engine:** StarRocks
---
### Bug description
Superset's SQL parser reformats queries before execution. During this
process,
inline `--` comments are converted to `/* */` block comments and
repositioned —
and when a query contains a `/*+ SET_VAR(...) */` optimizer hint, the
converted
comment gets **injected inside the hint block**, producing invalid SQL
syntax.
This causes a hard syntax error in StarRocks (and likely any engine that
uses
the `/*+ ... */` hint convention, such as MySQL or TiDB).
---
### How to reproduce
1. Connect Superset to a **StarRocks** database.
2. Open SQL Lab and run the following query:
```sql
SELECT /*+ SET_VAR(query_timeout = 3000) */ col1, col2
FROM my_table
LIMIT 100
-- increase timeout for large scans
```
3. Click **Run**.
---
### Expected behavior
The query should execute as written. The `--` comment is cosmetic and should
not affect the optimizer hint syntax. Expected SQL sent to StarRocks:
```sql
SELECT /*+ SET_VAR(query_timeout = 3000) */ col1, col2
FROM my_table
LIMIT 100
/* increase timeout for large scans */
```
Or with the comment stripped/moved safely outside the hint block.
---
### Actual behavior
Superset's SQL reformatter moves the `--` comment and injects it **inside**
the
optimizer hint block. The actual SQL sent to StarRocks becomes:
```sql
SELECT /*+ SET_VAR(query_timeout /* increase timeout for large scans */ =
3000) */ col1, col2
FROM my_table
LIMIT 100
```
StarRocks throws a syntax error because nested `/* */` inside `/*+ ... */`
is
not valid:
```
starrocks error: Getting syntax error at line 1, column 50. Detail message:
Unexpected input '=', the most similar input is {a legal identifier}.
```
---
### Root cause (hypothesis)
Superset passes SQL through `sqlglot` for parsing, pretty-printing, and
security checks (e.g. RLS injection, table extraction). During SQL
regeneration, `sqlglot`:
1. Converts `--` inline comments to `/* */` block comment nodes.
2. Re-attaches them to the nearest token — which in this case is **inside**
the optimizer hint block.
Since Superset does not have a dedicated StarRocks dialect in `sqlglot`, the
hint is treated as a generic comment, and comment repositioning corrupts it.
**Related:**
- PR #30350 — "fix: don't reformat generated queries"
- Issue #29466 — SQL with inline `--` comments fails after reformatting
- Issue #4412 — trailing `--` comments leaking into subqueries
---
### Screenshots / logs
<img width="1343" height="174" alt="Image"
src="https://github.com/user-attachments/assets/72326783-1c69-44ec-a38c-1ed8487722a6";
/>
---
### Workaround
Removing all `--` comments from queries that use `/*+ ... */` optimizer
hints
prevents the issue. This is not a sustainable fix for production use.
---
### Checklist
- [x] I have searched Superset docs and Slack and didn't find a solution to
my problem.
- [x] I have searched the GitHub issue tracker and didn't find a similar bug
report.
- [x] I have checked Superset's logs for errors and included relevant
details above.
---
### Screenshots/recordings
_No response_
### Superset version
6.0.0
### Python version
3.11
### Node version
Not applicable
### Browser
Chrome
### Additional context
_No response_
### Checklist
- [ ] I have searched Superset docs and Slack and didn't find a solution to
my problem.
- [ ] I have searched the GitHub issue tracker and didn't find a similar bug
report.
- [ ] I have checked Superset's logs for errors and if I found a relevant
Python stacktrace, I included it here as text in the "additional context"
section.
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