Fix byte position accounting in cached batch output

[fallintoplace]

No issue filed.

Description

Fix byte position accounting in the cached batch parquet output stream. OutputStream.write(int) writes one byte, so the tracked position should advance by one byte.

Checklists

Documentation

• Updated for new or modified user-facing features or behaviors
• No user-facing change

Testing

• Added or modified tests to cover new code paths
• Covered by existing tests
  (Please provide the names of the existing tests in the PR description.)
• Not required

Performance

• Tests ran and results are added in the PR description
• Issue filed with a link in the PR description
• Not required

[greptile-apps]

Greptile Summary

Fixes an off-by-factor-of-4 bug in the byte-position tracking of the ByteArrayOutputFile output stream used when serializing cached Parquet batches. OutputStream.write(int) writes exactly one byte (the low-order byte of the argument), so pos must advance by 1, not by Integer.BYTES (which is 4).

• The bug caused getPos() to return positions 4× too large on every single-byte write, potentially corrupting offset accounting in the Parquet encoder.
• The sibling overrides (write(byte[]) → b.length, write(byte[], int, int) → len) were already correct; only the write(int) path was wrong.

Confidence Score: 5/5

Single-line fix correcting an obvious mis-accounting; all three write paths now agree and the change is trivially verifiable against the Java OutputStream contract.

The change is a one-character correction to a clearly wrong constant. OutputStream.write(int) is documented to write exactly one byte, so replacing Integer.BYTES (4) with 1 is unambiguously correct. The sibling overrides were already right; no other logic is touched.

No files require special attention.

Important Files Changed

Filename	Overview
sql-plugin/src/main/scala/com/nvidia/spark/rapids/parquet/ParquetCachedBatchSerializer.scala	Corrects pos += Integer.BYTES to pos += 1 in the write(Int) override of the anonymous DelegatingPositionOutputStream; the fix is accurate and all three write overrides now consistently track bytes written.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant PE as Parquet Encoder
    participant POS as DelegatingPositionOutputStream
    participant BOS as ByteArrayOutputStream

    PE->>POS: write(b: Int)
    POS->>BOS: super.write(b) [writes 1 byte]
    Note over POS: pos += 1  ✅ (was Integer.BYTES = 4 ❌)
    PE->>POS: getPos(): Long
    POS-->>PE: pos (now accurate)

    PE->>POS: write(b: Array[Byte])
    POS->>BOS: super.write(b)
    Note over POS: pos += b.length ✅

    PE->>POS: write(b: Array[Byte], off: Int, len: Int)
    POS->>BOS: super.write(b, off, len)
    Note over POS: pos += len ✅

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sequenceDiagram
    participant PE as Parquet Encoder
    participant POS as DelegatingPositionOutputStream
    participant BOS as ByteArrayOutputStream

    PE->>POS: write(b: Int)
    POS->>BOS: super.write(b) [writes 1 byte]
    Note over POS: pos += 1  ✅ (was Integer.BYTES = 4 ❌)
    PE->>POS: getPos(): Long
    POS-->>PE: pos (now accurate)

    PE->>POS: write(b: Array[Byte])
    POS->>BOS: super.write(b)
    Note over POS: pos += b.length ✅

    PE->>POS: write(b: Array[Byte], off: Int, len: Int)
    POS->>BOS: super.write(b, off, len)
    Note over POS: pos += len ✅

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