Re: [SQLObject] Specifying defaultOrder

[Luke O. <lu...@me...>]

> > Sort order cannot currently be specified in SO.
>
> Should say something about the direction that development should be taking.
>
> Nick

Alright, here's what it'll take (from current CVS) to get order direction:

Questions:

Can you think of better names than "_defaultOrderDirection" and
"orderDirection"?

Should the value be the strings "DESC"/"ASC", be case-insensitive, be some
python representation of these strings? Accept strings but turn them into some
python rep?

1. Modify SQLObject to specify _defaultOrderDirection = None in class vars.

2. Modify SQLObject.select() to take keyword "orderDirection", and pass to
SelectResults.

    def select(cls, clause=None, clauseTables=None,
               orderBy=NoDefault, orderDirection=NoDefault,
               groupBy=None, limit=None, lazyColumns=False):
        return SelectResults(cls, clause, clauseTables=clauseTables,
                     orderBy=orderBy, orderDirection=orderDirection,
                     groupBy=groupBy, limit=limit, lazyColumns=lazyColumns)

3. Modify SelectResults (SQLObject.py) class to set ops['orderDirection'] =
sourceClass._defaultOrderDirection if not specified.

        if self.ops.get('orderDirection', NoDefault) is NoDefault:
            self.ops['orderDirection'] = sourceClass._defaultOrderDirection

4. Modify DBConnection.whereClauseForSelect() to actually insert the DESC/ASC
word if ops['orderDirection'] is set.

     if order and ops.get('dbOrderBy'):
         q = "%s ORDER BY %s" % (q, ", ".join(clauseList(ops['dbOrderBy'])))
+        if ops.get('orderDirection',None):
+            q = "%s %s" % (q, ops['orderDirection'])

(Also, DBMConnection implements it's own iterSelect/DBMSelectResults,
presumably because it doesn't support ORDER BY natively. This will need to be
modified to swap comparisons much like Joins below.)

4. Modify SOJoin.__init__() to accept an orderDirection keyword, modify
SOJoin._applyOrder() to use defaultSortClass._defaultOrderDirection if None
given, and to use a reverseSorter that swaps the comparison if
orderDirection.upper() == 'DESC'

    def _applyOrderBy(self, results, defaultSortClass):
        if self.orderBy is NoDefault:
            self.orderBy = defaultSortClass._defaultOrder
+       if self.orderDirection is NoDefault:
+           self.orderDirection = defaultSortClass._defaultOrderDirection
        if self.orderBy is not None:
            def sorter(a, b, attr=self.orderBy):
                return cmp(getattr(a, attr),
                           getattr(b, attr))
+           def revSorter(a, b, attr=self.orderBy):
+               return cmp(getattr(a, attr), getattr(b, attr))
+           if self.orderDirection.upper() == 'DESC'
                results.sort(revSorter)
+           else:
+               results.sort(sorter)
        return results


And I think that should be everything. I haven't tested all of this yet, and it
can't be committed till Ian returns, but comments are welcome.

- Luke