AlkantarClanX12
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from peewee import *
from playhouse.sqlite_ext import JSONField
class BaseChangeLog(Model):
timestamp = DateTimeField(constraints=[SQL('DEFAULT CURRENT_TIMESTAMP')])
action = TextField()
table = TextField()
primary_key = IntegerField()
changes = JSONField()
class ChangeLog(object):
# Model class that will serve as the base for the changelog. This model
# will be subclassed and mapped to your application database.
base_model = BaseChangeLog
# Template for the triggers that handle updating the changelog table.
# table: table name
# action: insert / update / delete
# new_old: NEW or OLD (OLD is for DELETE)
# primary_key: table primary key column name
# column_array: output of build_column_array()
# change_table: changelog table name
template = """CREATE TRIGGER IF NOT EXISTS %(table)s_changes_%(action)s
AFTER %(action)s ON %(table)s
BEGIN
INSERT INTO %(change_table)s
("action", "table", "primary_key", "changes")
SELECT
'%(action)s', '%(table)s', %(new_old)s."%(primary_key)s", "changes"
FROM (
SELECT json_group_object(
col,
json_array(
case when json_valid("oldval") then json("oldval")
else "oldval" end,
case when json_valid("newval") then json("newval")
else "newval" end)
) AS "changes"
FROM (
SELECT json_extract(value, '$[0]') as "col",
json_extract(value, '$[1]') as "oldval",
json_extract(value, '$[2]') as "newval"
FROM json_each(json_array(%(column_array)s))
WHERE "oldval" IS NOT "newval"
)
);
END;"""
drop_template = 'DROP TRIGGER IF EXISTS %(table)s_changes_%(action)s'
_actions = ('INSERT', 'UPDATE', 'DELETE')
def __init__(self, db, table_name='changelog'):
self.db = db
self.table_name = table_name
def _build_column_array(self, model, use_old, use_new, skip_fields=None):
# Builds a list of SQL expressions for each field we are tracking. This
# is used as the data source for change tracking in our trigger.
col_array = []
for field in model._meta.sorted_fields:
if field.primary_key:
continue
if skip_fields is not None and field.name in skip_fields:
continue
column = field.column_name
new = 'NULL' if not use_new else 'NEW."%s"' % column
old = 'NULL' if not use_old else 'OLD."%s"' % column
if isinstance(field, JSONField):
# Ensure that values are cast to JSON so that the serialization
# is preserved when calculating the old / new.
if use_old: old = 'json(%s)' % old
if use_new: new = 'json(%s)' % new
col_array.append("json_array('%s', %s, %s)" % (column, old, new))
return ', '.join(col_array)
def trigger_sql(self, model, action, skip_fields=None):
assert action in self._actions
use_old = action != 'INSERT'
use_new = action != 'DELETE'
cols = self._build_column_array(model, use_old, use_new, skip_fields)
return self.template % {
'table': model._meta.table_name,
'action': action,
'new_old': 'NEW' if action != 'DELETE' else 'OLD',
'primary_key': model._meta.primary_key.column_name,
'column_array': cols,
'change_table': self.table_name}
def drop_trigger_sql(self, model, action):
assert action in self._actions
return self.drop_template % {
'table': model._meta.table_name,
'action': action}
@property
def model(self):
if not hasattr(self, '_changelog_model'):
class ChangeLog(self.base_model):
class Meta:
database = self.db
table_name = self.table_name
self._changelog_model = ChangeLog
return self._changelog_model
def install(self, model, skip_fields=None, drop=True, insert=True,
update=True, delete=True, create_table=True):
ChangeLog = self.model
if create_table:
ChangeLog.create_table()
actions = list(zip((insert, update, delete), self._actions))
if drop:
for _, action in actions:
self.db.execute_sql(self.drop_trigger_sql(model, action))
for enabled, action in actions:
if enabled:
sql = self.trigger_sql(model, action, skip_fields)
self.db.execute_sql(sql)