diff options
Diffstat (limited to 'oslo_db/sqlalchemy/utils.py')
| -rw-r--r-- | oslo_db/sqlalchemy/utils.py | 33 |
1 files changed, 20 insertions, 13 deletions
diff --git a/oslo_db/sqlalchemy/utils.py b/oslo_db/sqlalchemy/utils.py index c5030a0..e628908 100644 --- a/oslo_db/sqlalchemy/utils.py +++ b/oslo_db/sqlalchemy/utils.py @@ -146,7 +146,8 @@ def paginate_query(query, model, limit, sort_keys, marker=None, the lexicographical ordering: (k1 > X1) or (k1 == X1 && k2 > X2) or (k1 == X1 && k2 == X2 && k3 > X3) - We also have to cope with different sort_directions. + We also have to cope with different sort_directions and cases where k2, + k3, ... are nullable. Typically, the id of the last row is used as the client-facing pagination marker, then the actual marker object must be fetched from the db and @@ -223,18 +224,24 @@ def paginate_query(query, model, limit, sort_keys, marker=None, criteria_list = [] for i in range(len(sort_keys)): crit_attrs = [] - for j in range(i): - model_attr = getattr(model, sort_keys[j]) - crit_attrs.append((model_attr == marker_values[j])) - - model_attr = getattr(model, sort_keys[i]) - if sort_dirs[i].startswith('desc'): - crit_attrs.append((model_attr < marker_values[i])) - else: - crit_attrs.append((model_attr > marker_values[i])) - - criteria = sqlalchemy.sql.and_(*crit_attrs) - criteria_list.append(criteria) + # NOTE: We skip the marker value comparison if marker_values[i] is + # None, for two reasons: 1) the comparison operators below + # ('<', '>') are not applicable on None value; 2) this is + # safe because we can assume the primary key is included in + # sort_key, thus checked as (one of) marker values. + if marker_values[i] is not None: + for j in range(i): + model_attr = getattr(model, sort_keys[j]) + crit_attrs.append((model_attr == marker_values[j])) + + model_attr = getattr(model, sort_keys[i]) + if sort_dirs[i].startswith('desc'): + crit_attrs.append((model_attr < marker_values[i])) + else: + crit_attrs.append((model_attr > marker_values[i])) + + criteria = sqlalchemy.sql.and_(*crit_attrs) + criteria_list.append(criteria) f = sqlalchemy.sql.or_(*criteria_list) query = query.filter(f) |