Antiproject

Filters out specified attributes of a relation.

Usage

antiproject (data, attributes : projected-data)

Details

Attributes are a comma-delimited list of attributes in the relation data that are retained in the projected-data.

Notes

All tuples other for the first in the attributes relation will be ignored.

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 test
      {
       INPUT: stream books
       OUTPUT: stream answer
      
       BODY
       {
         antiproject (books, "pub_date, pages" : answer)
       }
      }

will generate the following output:

      ----------------------------------------------
      RELATION: test_answer
         attrs: title, author
      ----------------------------------------------
      Title3|Author2
      Title2|Author2
      Title5|Author2
      Title4|Author3
      Title1|Author1
      ----------------------------------------------