question: int readPartition ( ByteSequencesReader reader ) throws IOException { long start = System . currentTimeMillis ( ) ; if ( valueLength != - 1 ) { int limit = ramBufferSize . bytes / valueLength ; for ( int i = 0 ; i < limit ; i ++ ) { BytesRef item = null ; try { item = reader . next ( ) ; } catch ( Throwable t ) { verifyChecksum ( t , reader ) ; } if ( item == null ) { break ; } buffer . append ( item ) ; } } else { while ( true ) { BytesRef item = null ; try { item = reader . next ( ) ; } catch ( Throwable t ) { verifyChecksum ( t , reader ) ; } if ( item == null ) { break ; } buffer . append ( item ) ; if ( bufferBytesUsed . get ( ) > ramBufferSize . bytes ) { break ; } } } sortInfo . readTime += System . currentTimeMillis ( ) - start ; return buffer . size ( ) ; }
target:  Read in a single partition of data 