iterator
Class Sort

java.lang.Object
  iterator.Iterator
      iterator.Sort

All Implemented Interfaces:

Flags, GlobalConst

public class Sort

extends Iterator

implements GlobalConst

The Sort class sorts a file. All necessary information are passed as arguments to the constructor. After the constructor call, the user can repeatly call get_next() to get tuples in sorted order. After the sorting is done, the user should call close() to clean up.

Field Summary

Fields inherited from class iterator.Iterator

closeFlag

Fields inherited from interface global.GlobalConst

INVALID_PAGE, MAX_NAME, MAX_SPACE, MAXATTRNAME, MAXFILENAME, MAXINDEXNAME, MINIBASE_BUFFER_POOL_SIZE, MINIBASE_DB_SIZE, MINIBASE_DEFAULT_SHAREDMEM_SIZE, MINIBASE_MAX_TRANSACTIONS, MINIBASE_MAXARRSIZE, MINIBASE_PAGESIZE, NUMBUF

Fields inherited from interface global.Flags

DEBUG, TEST

Constructor Summary

Sort(AttrType[] in, short len_in, short[] str_sizes, Iterator am, int sort_fld, TupleOrder sort_order, int sort_fld_len, int n_pages)
Class constructor, take information about the tuples, and set up the sorting

Method Summary

void	close() Cleaning up, including releasing buffer pages from the buffer pool and removing temporary files from the database.
Tuple	get_next() Returns the next tuple in sorted order.

Methods inherited from class iterator.Iterator

free_buffer_pages, get_buffer_pages

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Sort

public Sort(AttrType[] in,
            short len_in,
            short[] str_sizes,
            Iterator am,
            int sort_fld,
            TupleOrder sort_order,
            int sort_fld_len,
            int n_pages)
     throws java.io.IOException,
            SortException

Class constructor, take information about the tuples, and set up the sorting

Parameters:

in - array containing attribute types of the relation

len_in - number of columns in the relation

str_sizes - array of sizes of string attributes

am - an iterator for accessing the tuples

sort_fld - the field number of the field to sort on

sort_order - the sorting order (ASCENDING, DESCENDING)

n_pages - amount of memory (in pages) available for sorting

Throws:

java.io.IOException - from lower layers

SortException - something went wrong in the lower layer.

Method Detail

get_next

public Tuple get_next()
               throws java.io.IOException,
                      SortException,
                      UnknowAttrType,
                      LowMemException,
                      JoinsException,
                      java.lang.Exception

Returns the next tuple in sorted order. Note: You need to copy out the content of the tuple, otherwise it will be overwritten by the next get_next() call.

Specified by:

get_next in class Iterator

Returns:

the next tuple, null if all tuples exhausted

Throws:

java.io.IOException - from lower layers

SortException - something went wrong in the lower layer.

JoinsException - from generate_runs().

UnknowAttrType - attribute type unknown

LowMemException - memory low exception

java.lang.Exception - other exceptions

close

public void close()
           throws SortException,
                  java.io.IOException

Cleaning up, including releasing buffer pages from the buffer pool and removing temporary files from the database.

Specified by:

close in class Iterator

Throws:

java.io.IOException - from lower layers

SortException - something went wrong in the lower layer.