Distinct

Emits unique tuples of relation.

Usage

distinct (indata, criteria : outdata)

Details

If each tuple of indata is unique for the criteria attributes, then that tuple is admitted as outdata.

Notes

None.

Known Bugs

None.

Example

Using the input:

      RELATION books: title char, author char, pub_date date, pages number
      Title1|Author1|09-01-1991|34
      Title2|Author2|12-23-1954|479
      Title3|Author2|05-09-2002|733
      Title4|Author3|01-01-1968|32
      Title5|Author2|07-03-2001|1152

when executing the plan:

      PLAN udistinct1
      {
        INPUT: stream books
        OUTPUT: stream answer

        BODY
        {
          project (books, "author" : p-books)
          distinct (p-books, "author" : answer)
        }
      }

will generate the following output:

      ----------------------------------------------
      RELATION: test_answer
         attrs: author
      ----------------------------------------------
      Author2
      Author1
      Author3
      ----------------------------------------------