Prathamesh9284 commented on issue #690:
URL: https://github.com/apache/wayang/issues/690#issuecomment-3914300188
Hi @zkaoudi
````markdown
### Root Cause
In `WayangTableScanVisitor.java` (line 67), the `fieldTypes` list is built
using:
```java
wayangRelNode.getRowType()
````
This returns the **RelNode’s row type**, which in certain cases may contain
fewer fields than the actual table schema (e.g., when Calcite optimizes away
unused columns).
However, the CSV source always reads **all columns from disk**, leading to a
mismatch between `tokens.length` and `fieldTypes.size()`, which causes runtime
issues.
---
### Proposed Fix
Update line 67 in `WayangTableScanVisitor.java`:
**From:**
```java
final List<RelDataType> fieldTypes =
wayangRelNode.getRowType().getFieldList().stream()
```
**To:**
```java
final List<RelDataType> fieldTypes =
wayangRelNode.getTable().getRowType().getFieldList().stream()
```
Using `getTable().getRowType()` ensures we always retrieve the full table
schema, which aligns with how `getColumnNames()` is implemented in
`WayangTableScan.java` (line 98).
Column pruning is still correctly handled downstream by the `WayangProject`
operator via a `MapOperator`.
---
### Testing
I added a regression test using Mockito that:
* Simulates a `WayangTableScan` with a trimmed row type (1 field)
* While the underlying table schema contains 4 fields
* Reproduces the exact scenario described in this issue
The test:
* Fails before the fix
* Passes after applying the fix
* All existing tests continue to pass
---
If this approach looks correct, I’ll proceed with opening a PR including the
fix and the regression test.
Looking forward to feedback!
```
```
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