Databases

[:days4/projects/: Other SAGE Days 4 Projects]

Robert Miller, Emily Kirkman, Tom Boothby, David Joyner, Yi Qiang

GOAL: SAGE Enhancement Proposal.

• Database class
  • instance field
    • filename -- the database itself
    • connection -- a pysqlite connection to 'filename'
    • query string -- this would be a string representing the 'query state' of the database object.
      • allows for recursive searching quickly, since we can simply modify the string, and wait until we have to execute the query
    • dict of tables -- keyed by table name, entries are
      • dict of columns -- keyed by column name, keeps track of indices, primary key state
    • mutable -- boolean
  • functions
    • create/drop table
    • create/drop column( column name, table, bool index=False, bool primary key=False )
      • if no table specified, raise an error and educate user about sql
    • create/drop index( column, table(s) )
    • create/drop primary key( column, table )
      • QUESTION: should we allow multiple tables? bounce this off someone who knows (i.e. is it possible to do this with sqlite?)
    • create/drop row( table, dict )
      • create accepts a dictionary keyed by column name

        • def foo(table=None, **kwds):
              if table is None:
                  raise KeyError('Table must be specified')
              print kwds
          
          sage: foo(table='table_name', shit='poo', dog='cat')
          # works
          sage: foo(shit='poo', dog='cat')
          Exception (click to the left for traceback):
          ...
          KeyError: 'Table must be specified'

    • add data from whatever (e.g. quickly via sql file): magic function to deal with other ways to add data? think about this more later.
    • copy
      • creates a new db and everything (completely deep copy)
      • preserves the query string?
      • executes the query string first?

      • is it possible to have multiple connections to the same .db file? [http://www.mail-archive.com/sqlite-users@sqlite.org/msg24725.html relevant]

• unified Database class
  • recursive queries without actually calling sqlite every time: queries kept track of by a string...
  • exactly what should the following do?

    • D = Database('something.db')
      Q = D.query({'number_of_finches' : 7}, inplace=False) # hypothetical way to query

    • proposal: it should create a new Database object, with a separate connection to the same database, and add "number_of_finches = 7" to the query string

      D = Database('something.db')
      D.query({'number_of_finches' : 7}, inplace=True) # hypothetical way to query

    • proposal: it should add "number_of_finches = 7" to the query string
  • init establishes connection to sqlite

    •  D = Database()  creates a new temp database and opens a connection to it

    •  D = Database('existing.db')  opens a connection to 'existing.db'

  • create, remove and modify tables
  • print?
    • should probably just print a string with database name, number of tables...?
  • save

    •  D.save('my.db')  should copy the class's database file to my.db.

    • should this execute queries first?
  • show
    • for extensions to the Database class, this can be anything, e.g. graph database prints nice table

    • for default database class, what would this do? execute any queries and print the data?

  • clear_queries
• Brainless database creation.
• Databases distributed with sage: Standard databases included with sage should be immutable
• Online databases
  • cgi web-accessible...
  • accessible from SAGE, perhaps hosted at sage.math...
  • SQLite servers?
• Automagic caching: keep track of computation results
  • keeping those results in portable objects, making these objects merge-able, etc...

• Licensing: ∃ DBGPL?

• Noticing identical database entries

• SAGE [http://www.initd.org/pub/software/pysqlite/doc/usage-guide.html interface] to sqlite [:sqlite-tutorial: creating your own database using sqlite in sage]