def datetime_range(
lower=datetime.now(tz=timezone.utc), upper=None, nullable=False):
"""Postgres DateTime Range column mapping.
"""
return sa.Column(postgresql.TSTZRANGE(),
default=pg_extras.DateTimeTZRange(lower, upper),
nullable=nullable)
def make_clock(effective_lower: dt.datetime, vclock_lower: int,
**kwargs) -> _ClockSet:
"""construct a clock set tuple"""
effective_upper = kwargs.get('effective_upper', None)
vclock_upper = kwargs.get('vclock_upper', None)
effective = psql_extras.DateTimeTZRange(effective_lower,
effective_upper)
vclock = psql_extras.NumericRange(vclock_lower, vclock_upper)
return _ClockSet(effective, vclock)
def effective_now():
"""UTC DateTime Range starting from now.
"""
utc_now = datetime.now(tz=timezone.utc)
return pg_extras.DateTimeTZRange(utc_now.date(), None)
def effective_now() -> psql_extras.DateTimeTZRange:
utc_now = dt.datetime.now(tz=dt.timezone.utc)
return psql_extras.DateTimeTZRange(utc_now, None)
def _record_history(self, clocked: Clocked):
"""
Record all history for a given clocked object
Args:
clocked (Clocked): instance of clocked object
"""
#
# Check for activity misuse
#
if clocked.temporal_options.activity_model is not None and clocked.activity is None:
raise ValueError('An activity is required when saving a %s' %
type(clocked).__name__)
if clocked.temporal_options.activity_model is None and clocked.activity is not None:
raise ValueError(
'There is no activity model for %s; you cannot supply an activity'
% type(clocked).__name__)
#
# Determine which fields have changed
#
changed_fields = {}
for field, history_model in self.history_models.items():
new_val = clocked._meta.get_field(field).value_from_object(clocked)
prev_val = clocked._state._django_temporal_previous[field]
if new_val != prev_val or clocked._state._django_temporal_add:
changed_fields[(field, history_model)] = new_val
if not changed_fields:
return
#
# Increment the clock and build the effective and vclock ranges for the next tick
#
timestamp = timezone.now()
clocked.vclock += 1
new_tick = clocked.vclock
#
# Create the EntityClock for this tick
#
clock_model = type(clocked).temporal_options.clock_model
if clocked.temporal_options.activity_model is not None:
clock = clock_model(entity=clocked,
activity=clocked.activity,
tick=new_tick)
else:
clock = clock_model(entity=clocked, tick=new_tick)
clock.save()
#
# Create the field history for this tick
#
for (field, history_model), new_val in changed_fields.items():
if new_tick > 1:
# This is an update, not a create, so update the upper bounds of the previous tick.
#
# This cannot be done with F expressions because of the range updates, unless we write our
# own implementations of int4range/tstzrange.
#
# Instead use .raw and force execution by wrapping with list(). This approach ensures that
# the update happens in the correct connection/transaction.
list(
history_model.objects.raw(
""" UPDATE {table_name}
SET vclock = int4range(lower(vclock), %s),
effective = tstzrange(lower(effective), %s)
WHERE entity_id = %s AND upper(vclock) IS NULL
RETURNING id;
""".format(table_name=connection.ops.quote_name(
history_model._meta.db_table)),
[new_tick, timestamp, clocked.pk]))
hist = history_model(**{field: new_val},
entity=clocked,
vclock=psql_extras.NumericRange(
new_tick, None),
effective=psql_extras.DateTimeTZRange(
timestamp, None))
hist.save()
# Update the stored state for this field to detect future changes
clocked._state._django_temporal_previous[field] = new_val
# Reset the activity so it can't be accidentally reused easily
clocked.activity = None
# Update the vclock value without triggering a recursive `record_history`
type(clocked).objects \
.filter(**{clocked._meta.pk.name: getattr(clocked, clocked._meta.pk.name)}) \
.update(vclock=new_tick)
