fix: handle invalid byte ranges in calculate_range for single-line files (#19607)

## Which issue does this PR close?

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- Closes #19605.

## Rationale for this change

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in the issue then this section is not needed.
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The `calculate_range` function creates invalid byte ranges (where `start
> end`) when reading single-line CSV/JSON files that are split into
multiple partitions. This causes an error like:

```
ObjectStore(Generic { store: "S3", source: Inconsistent { start: 1149247, end: 1149246 } })
```

When `find_first_newline` doesn't find a newline (single-line file), it
returns the remaining file length. This causes `start + start_delta` to
exceed `end + end_delta`, creating an invalid range. The current check
only handles `range.start == range.end`, not `range.start > range.end`.


## What changes are included in this PR?

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is sometimes worth providing a summary of the individual changes in this
PR.
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1. Added an early termination check after computing `start_delta`: if
the first newline after `start` is beyond the partition boundary (`start
+ start_delta > end`), return `TerminateEarly` since no complete records
exist in this partition.

2. Changed the final range validation from `==` to `>=` as a safety net
for edge cases.

3. Added a regression test that reproduces the bug with a single-line
file split into partitions.

## Are these changes tested?

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Yes, added `test_calculate_range_single_line_file` which:
- Creates a single-line JSON file without new-lines
- Simulates partition 2 (middle to end of file)
- Verifies that `calculate_range` returns `TerminateEarly` instead of an
invalid range

## Are there any user-facing changes?

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No

Author: vigimite

datafusion/datasource/src/mod.rs

@@ -350,6 +350,10 @@ pub async fn calculate_range(
                 0
             };
 
+            if start + start_delta > end {
+                return Ok(RangeCalculation::TerminateEarly);
+            }
+
             let end_delta = if end != file_size {
                 find_first_newline(store, location, end - 1, file_size, newline).await?
             } else {
@@ -358,7 +362,7 @@ pub async fn calculate_range(
 
             let range = start + start_delta..end + end_delta;
 
-            if range.start == range.end {
+            if range.start >= range.end {
                 return Ok(RangeCalculation::TerminateEarly);
             }
 
@@ -723,4 +727,31 @@ mod tests {
         // testing an empty path with `ignore_subdirectory` set to false
         assert!(url.contains(&Path::parse("/var/data/mytable/").unwrap(), false));
     }
+
+    /// Regression test for <https://github.com/apache/datafusion/issues/19605>
+    #[tokio::test]
+    async fn test_calculate_range_single_line_file() {
+        use super::{PartitionedFile, RangeCalculation, calculate_range};
+        use object_store::ObjectStore;
+        use object_store::memory::InMemory;
+
+        let content = r#"{"id":1,"data":"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"}"#;
+        let file_size = content.len() as u64;
+
+        let store: Arc<dyn ObjectStore> = Arc::new(InMemory::new());
+        let path = Path::from("test.json");
+        store.put(&path, content.into()).await.unwrap();
+
+        let mid = file_size / 2;
+        let partitioned_file = PartitionedFile::new_with_range(
+            path.to_string(),
+            file_size,
+            mid as i64,
+            file_size as i64,
+        );
+
+        let result = calculate_range(&partitioned_file, &store, None).await;
+
+        assert!(matches!(result, Ok(RangeCalculation::TerminateEarly)));
+    }
 }