Commit d3c2eb10 authored by Anssi Kääriäinen's avatar Anssi Kääriäinen
Browse files

Fixed #18330 - Made cache culling 3rd party db backend friendly 

This is Ian Kelly's patch from #15580 with minor modifications.
parent 0f49b2bc

django/core/cache/backends/db.py

+3 −11
Original line number Diff line number Diff line
@@ -167,17 +167,9 @@ class DatabaseCache(BaseDatabaseCache): 
            num = cursor.fetchone()[0]

            if num > self._max_entries:

                cull_num = num / self._cull_frequency

                if connections[db].vendor == 'oracle':

                    # Oracle doesn't support LIMIT + OFFSET

                    cursor.execute("""SELECT cache_key FROM

(SELECT ROW_NUMBER() OVER (ORDER BY cache_key) AS counter, cache_key FROM %s)

WHERE counter > %%s AND COUNTER <= %%s""" % table, [cull_num, cull_num + 1])

                else:

                    # This isn't standard SQL, it's likely to break

                    # with some non officially supported databases

                    cursor.execute("SELECT cache_key FROM %s "

                                   "ORDER BY cache_key "

                                   "LIMIT 1 OFFSET %%s" % table, [cull_num])

                cursor.execute(

                    connections[db].ops.cache_key_culling_sql() % table,

                    [cull_num])

                cursor.execute("DELETE FROM %s "

                               "WHERE cache_key < %%s" % table,

                               [cursor.fetchone()[0]])

django/db/backends/__init__.py

+10 −0
Original line number Diff line number Diff line
@@ -475,6 +475,16 @@ class BaseDatabaseOperations(object): 
        """

        return None



    def cache_key_culling_sql(self):

        """

        Returns a SQL query that retrieves the first cache key greater than the

        n smallest.



        This is used by the 'db' cache backend to determine where to start

        culling.

        """

        return "SELECT cache_key FROM %s ORDER BY cache_key LIMIT 1 OFFSET %%s"



    def date_extract_sql(self, lookup_type, field_name):

        """

        Given a lookup_type of 'year', 'month' or 'day', returns the SQL that

django/db/backends/oracle/base.py

+7 −0
Original line number Diff line number Diff line
@@ -118,6 +118,13 @@ WHEN (new.%(col_name)s IS NULL) 
/""" % locals()

        return sequence_sql, trigger_sql



    def cache_key_culling_sql(self):

        return """

            SELECT cache_key

              FROM (SELECT cache_key, rank() OVER (ORDER BY cache_key) AS rank FROM %s)

             WHERE rank = %%s + 1

        """



    def date_extract_sql(self, lookup_type, field_name):

        # http://download-east.oracle.com/docs/cd/B10501_01/server.920/a96540/functions42a.htm#1017163

        if lookup_type == 'week_day':