app/django/db/models/sql/datastructures.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Tue, 27 Jan 2009 21:56:32 +0000
changeset 1015 b9d51be5104a
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Add profiling support to Melange. By assigning profile_main_as_logs or profile_main_as_html to main variable you can turn on profiling. profile_main_as_logs will log profile data to App Engine console logs, profile_main_as_html will show profile data as html at the bottom of the page. If you want to profile app on deployed app just set the profiling function and deploy it. Patch by: Pawel Solyga Reviewed by: to-be-reviewed

"""
Useful auxilliary data structures for query construction. Not useful outside
the SQL domain.
"""

class EmptyResultSet(Exception):
    pass

class FullResultSet(Exception):
    pass

class MultiJoin(Exception):
    """
    Used by join construction code to indicate the point at which a
    multi-valued join was attempted (if the caller wants to treat that
    exceptionally).
    """
    def __init__(self, level):
        self.level = level

class Empty(object):
    pass

class RawValue(object):
    def __init__(self, value):
        self.value = value

class Aggregate(object):
    """
    Base class for all aggregate-related classes (min, max, avg, count, sum).
    """
    def relabel_aliases(self, change_map):
        """
        Relabel the column alias, if necessary. Must be implemented by
        subclasses.
        """
        raise NotImplementedError

    def as_sql(self, quote_func=None):
        """
        Returns the SQL string fragment for this object.

        The quote_func function is used to quote the column components. If
        None, it defaults to doing nothing.

        Must be implemented by subclasses.
        """
        raise NotImplementedError

class Count(Aggregate):
    """
    Perform a count on the given column.
    """
    def __init__(self, col='*', distinct=False):
        """
        Set the column to count on (defaults to '*') and set whether the count
        should be distinct or not.
        """
        self.col = col
        self.distinct = distinct

    def relabel_aliases(self, change_map):
        c = self.col
        if isinstance(c, (list, tuple)):
            self.col = (change_map.get(c[0], c[0]), c[1])

    def as_sql(self, quote_func=None):
        if not quote_func:
            quote_func = lambda x: x
        if isinstance(self.col, (list, tuple)):
            col = ('%s.%s' % tuple([quote_func(c) for c in self.col]))
        elif hasattr(self.col, 'as_sql'):
            col = self.col.as_sql(quote_func)
        else:
            col = self.col
        if self.distinct:
            return 'COUNT(DISTINCT %s)' % col
        else:
            return 'COUNT(%s)' % col

class Date(object):
    """
    Add a date selection column.
    """
    def __init__(self, col, lookup_type, date_sql_func):
        self.col = col
        self.lookup_type = lookup_type
        self.date_sql_func = date_sql_func

    def relabel_aliases(self, change_map):
        c = self.col
        if isinstance(c, (list, tuple)):
            self.col = (change_map.get(c[0], c[0]), c[1])

    def as_sql(self, quote_func=None):
        if not quote_func:
            quote_func = lambda x: x
        if isinstance(self.col, (list, tuple)):
            col = '%s.%s' % tuple([quote_func(c) for c in self.col])
        else:
            col = self.col
        return self.date_sql_func(self.lookup_type, col)