# Fix Parquet EOF Error by Removing ByteBufferReadable Interface

## Summary

Fixed `EOFException: Reached the end of stream. Still have: 78 bytes left` error when reading Parquet files with complex schemas in Spark.

## Root Cause

`SeaweedHadoopInputStream` declared it implemented `ByteBufferReadable` interface but didn't properly implement it, causing incorrect buffering strategy and position tracking issues during positioned reads (critical for Parquet).

## Solution

Removed `ByteBufferReadable` interface from `SeaweedHadoopInputStream` to match Hadoop's `RawLocalFileSystem` pattern, which uses `BufferedFSInputStream` for proper position tracking.

## Changes

### Core Fix

1. **`SeaweedHadoopInputStream.java`**:
   - Removed `ByteBufferReadable` interface
   - Removed `read(ByteBuffer)` method
   - Cleaned up debug logging
   - Added documentation explaining the design choice

2. **`SeaweedFileSystem.java`**:
   - Changed from `BufferedByteBufferReadableInputStream` to `BufferedFSInputStream`
   - Applies to all streams uniformly
   - Cleaned up debug logging

3. **`SeaweedInputStream.java`**:
   - Cleaned up debug logging

### Cleanup

4. **Deleted debug-only files**:
   - `DebugDualInputStream.java`
   - `DebugDualInputStreamWrapper.java`
   - `DebugDualOutputStream.java`
   - `DebugMode.java`
   - `LocalOnlyInputStream.java`
   - `ShadowComparisonStream.java`

5. **Reverted**:
   - `SeaweedFileSystemStore.java` (removed all debug mode logic)

6. **Cleaned**:
   - `docker-compose.yml` (removed debug environment variables)
   - All `.md` documentation files in `test/java/spark/`

## Testing

All Spark integration tests pass:
- ✅ `SparkSQLTest.testCreateTableAndQuery` (complex 4-column schema)
- ✅ `SimpleOneColumnTest` (basic operations)
- ✅ All other Spark integration tests

## Technical Details

### Why This Works

Hadoop's `RawLocalFileSystem` uses the exact same pattern:
- Does NOT implement `ByteBufferReadable`
- Uses `BufferedFSInputStream` for buffering
- Properly handles positioned reads with automatic position restoration

### Position Tracking

`BufferedFSInputStream` implements positioned reads correctly:
```java
public int read(long position, byte[] buffer, int offset, int length) {
    long oldPos = getPos();
    try {
        seek(position);
        return read(buffer, offset, length);
    } finally {
        seek(oldPos);  // Restores position!
    }
}
```

This ensures buffered reads don't permanently change the stream position, which is critical for Parquet's random access pattern.

### Performance Impact

Minimal to none:
- Network latency dominates for remote storage
- Buffering is still active (4x buffer size)
- Extra byte[] copy is negligible compared to network I/O

## Commit Message

```
Fix Parquet EOF error by removing ByteBufferReadable interface

SeaweedHadoopInputStream incorrectly declared ByteBufferReadable interface
without proper implementation, causing position tracking issues during
positioned reads. This resulted in "78 bytes left" EOF errors when reading
Parquet files with complex schemas in Spark.

Solution: Remove ByteBufferReadable and use BufferedFSInputStream (matching
Hadoop's RawLocalFileSystem pattern) which properly handles position
restoration for positioned reads.

Changes:
- Remove ByteBufferReadable interface from SeaweedHadoopInputStream
- Change SeaweedFileSystem to use BufferedFSInputStream for all streams
- Clean up debug logging
- Delete debug-only classes and files

Tested: All Spark integration tests pass
```

## Files Changed

### Modified
- `other/java/hdfs3/src/main/java/seaweed/hdfs/SeaweedHadoopInputStream.java`
- `other/java/hdfs3/src/main/java/seaweed/hdfs/SeaweedFileSystem.java`
- `other/java/client/src/main/java/seaweedfs/client/SeaweedInputStream.java`
- `test/java/spark/docker-compose.yml`

### Reverted
- `other/java/hdfs3/src/main/java/seaweed/hdfs/SeaweedFileSystemStore.java`

### Deleted
- `other/java/hdfs3/src/main/java/seaweed/hdfs/DebugDualInputStream.java`
- `other/java/hdfs3/src/main/java/seaweed/hdfs/DebugDualInputStreamWrapper.java`
- `other/java/hdfs3/src/main/java/seaweed/hdfs/DebugDualOutputStream.java`
- `other/java/hdfs3/src/main/java/seaweed/hdfs/DebugMode.java`
- `other/java/hdfs3/src/main/java/seaweed/hdfs/LocalOnlyInputStream.java`
- `other/java/hdfs3/src/main/java/seaweed/hdfs/ShadowComparisonStream.java`
- All `.md` files in `test/java/spark/` (debug documentation)