code: int finalizeBuildPhase(IOManager ioAccess, FileIOChannel.Enumerator probeChannelEnumerator) throws IOException {
  		this.finalBufferLimit = this.buildSideWriteBuffer.getCurrentPositionInSegment();
  		this.partitionBuffers = this.buildSideWriteBuffer.close();
  
  		if (!isInMemory()) {
  			// close the channel.
  			this.buildSideChannel.close();
  
  			this.probeSideBuffer = FileChannelUtil.createOutputView(
  					ioAccess,
  					probeChannelEnumerator.next(),
  					compressionEnable,
  					compressionCodecFactory,
  					compressionBlockSize,
  					memorySegmentSize);
  			return 1;
  		} else {
  			return 0;
  		}
  	}
docs: After build phase.
  @return build spill return buffer, if have spilled, it returns the current write buffer,
  because it was used all the time in build phase, so it can only be returned at this time.