ggjh-159 opened a new issue, #12249:
URL: https://github.com/apache/gluten/issues/12249
### Backend
VL (Velox)
### Bug description
# Bug: VARCHAR literal value includes charset prefix `_UTF-16LE'...'` in
output
## Problem
When a SQL query contains VARCHAR string literals (e.g., `CASE WHEN ... THEN
'nightTime'`), the
output produced by Gluten-Flink includes an unexpected charset prefix
`_UTF-16LE'...'` around the
string value. For example, `'nightTime'` is rendered as
`_UTF-16LE'nightTime'` in the Print
connector output.
Native Flink (without Gluten) outputs the correct plain string value
`nightTime`.
## Root Cause
In `RexNodeConverter.toVariant()`, the VARCHAR branch calls
`literal.getValue().toString()`. For
VARCHAR type, `RexLiteral.getValue()` returns a Calcite `NlsString` object.
`NlsString.toString()`
produces the SQL literal format with charset prefix: `_UTF-16LE'value'`, not
the raw string value.
The CHAR branch in the same method uses the correct API:
`literal.getValueAs(String.class)`, which
returns the plain string value.
## File
-
`gluten-flink/planner/src/main/java/org/apache/gluten/rexnode/RexNodeConverter.java`,
line 113
## Verification: Native Flink does NOT have this issue
Tested the same q14 query on native Flink (without Gluten JARs), the output
is correct with no
charset prefix:
```
+I[1000, 2001, 26353920.936, nightTime, 2026-06-05T05:55:55.858, ..., 0]
```
This confirms the `_UTF-16LE` prefix is introduced by Gluten's planner, not
by Flink itself.
## Reproduce
Run any nexmark query with VARCHAR string literals in CASE WHEN expressions,
e.g., nexmark q14:
```sql
SELECT
auction, bidder, 0.908 * price as price,
CASE
WHEN HOUR(dateTime) >= 8 AND HOUR(dateTime) <= 18 THEN 'dayTime'
WHEN HOUR(dateTime) <= 6 OR HOUR(dateTime) >= 20 THEN 'nightTime'
ELSE 'otherTime'
END AS bidTimeType,
dateTime, extra,
count_char(extra, 'c') AS c_counts
FROM bid
WHERE 0.908 * price > 1000000 AND 0.908 * price < 50000000
```
### Actual output (Gluten-Flink)
```
+I[1012, 2001, 28428278.716, _UTF-16LE'nightTime', 2026-06-05T02:24:06.630,
..., 0]
```
### Expected output (native Flink)
```
+I[1012, 2001, 28428278.716, nightTime, 2026-06-05T02:24:06.630, ..., 0]
```
## Environment
- Gluten-Flink: 1.7.0-SNAPSHOT
- Flink: 1.19.2
### Gluten version
_No response_
### Spark version
None
### Spark configurations
_No response_
### System information
_No response_
### Relevant logs
```bash
```
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