def check_expression_support(self, expression):
bad_fields = (fields.DateField, fields.DateTimeField, fields.TimeField)
bad_aggregates = (
aggregates.Sum,
aggregates.Avg,
aggregates.Variance,
aggregates.StdDev,
)
if isinstance(expression, bad_aggregates):
for expr in expression.get_source_expressions():
try:
output_field = expr.output_field
except FieldError:
# Not every subexpression has an output_field which is fine
# to ignore.
pass
else:
if isinstance(output_field, bad_fields):
raise utils.NotSupportedError(
"You cannot use Sum, Avg, StdDev, and Variance "
"aggregations on date/time fields in sqlite3 "
"since date/time is saved as text.")
if (isinstance(expression, aggregates.Aggregate)
and len(expression.source_expressions) > 1):
raise utils.NotSupportedError(
"SQLite doesn't support DISTINCT on aggregate functions "
"accepting multiple arguments.")
def for_update_sql(self, nowait=False, skip_locked=False, of=()):
"""
Return the FOR UPDATE SQL clause to lock rows for an update operation.
"""
# DB2 doesn't support nowait select for update
if nowait:
raise utils.NotSupportedError(
"NOWAIT clause not supported by Db2 for iSeries")
return 'FOR UPDATE%s%s' % (
' OF %s' % ', '.join(of) if of else '',
' SKIP LOCKED DATA' if skip_locked else '',
)
def check_expression_support(self, expression):
bad_fields = (fields.DateField, fields.DateTimeField, fields.TimeField)
bad_aggregates = (aggregates.Sum, aggregates.Avg, aggregates.Variance,
aggregates.StdDev)
if isinstance(expression, bad_aggregates):
for expr in expression.get_source_expressions():
try:
output_field = expr.output_field
except FieldError:
# Not every subexpression has an output_field which is fine
# to ignore.
pass
else:
if isinstance(output_field, bad_fields):
raise utils.NotSupportedError(
'You cannot use Sum, Avg, StdDev, and Variance '
'aggregations on date/time fields in sqlite3 '
'since date/time is saved as text.')
def disable_constraint_checking(self):
raise utils.NotSupportedError(
"Db2 for iSeries currently supports no method of disabling constraints on a per-session basis."
)
