Support cascade deletion
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WQY\qiong
280
api/database.py
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280
api/database.py
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@@ -0,0 +1,280 @@
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from typing import Any
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from psycopg.rows import dict_row, Row
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from .connection import g_conn_dict as conn
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API_ADD = 'add'
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API_UPDATE = 'update'
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API_DELETE = 'delete'
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g_add_prefix = { 'operation': API_ADD }
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g_update_prefix = { 'operation': API_UPDATE }
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g_delete_prefix = { 'operation': API_DELETE }
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class ChangeSet:
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def __init__(self, ps: dict[str, Any] | None = None):
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self.operations : list[dict[str, Any]] = []
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if ps != None:
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self.append(ps)
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@staticmethod
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def from_list(ps: list[dict[str, Any]]):
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cs = ChangeSet()
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for _cs in ps:
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cs.append(_cs)
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return cs
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def add(self, ps: dict[str, Any]):
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self.operations.append(g_add_prefix | ps)
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return self
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def update(self, ps: dict[str, Any]):
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self.operations.append(g_update_prefix | ps)
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return self
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def delete(self, ps: dict[str, Any]):
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self.operations.append(g_delete_prefix | ps)
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return self
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def append(self, ps: dict[str, Any]):
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self.operations.append(ps)
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return self
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def merge(self, cs):
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if len(cs.operations) > 0:
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self.operations += cs.operations
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return self
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def dump(self):
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for op in self.operations:
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print(op)
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def compress(self):
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return self
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class DbChangeSet:
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def __init__(self, redo_sql: str, undo_sql: str, redo_cs: list[dict[str, Any]], undo_cs: list[dict[str, Any]]) -> None:
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self.redo_sql = redo_sql
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self.undo_sql = undo_sql
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self.redo_cs = redo_cs
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self.undo_cs = undo_cs
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@staticmethod
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def from_list(css):
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redo_sql_s : list[str] = []
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undo_sql_s : list[str] = []
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redo_cs_s : list[dict[str, Any]] = []
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undo_cs_s : list[dict[str, Any]] = []
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for r in css:
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redo_sql_s.append(r.redo_sql)
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undo_sql_s.append(r.undo_sql)
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redo_cs_s += r.redo_cs
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r.undo_cs.reverse() # reverse again...
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undo_cs_s += r.undo_cs
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redo_sql = '\n'.join(redo_sql_s)
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undo_sql_s.reverse()
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undo_sql = '\n'.join(undo_sql_s)
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undo_cs_s.reverse()
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return DbChangeSet(redo_sql, undo_sql, redo_cs_s, undo_cs_s)
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def read(name: str, sql: str) -> Row:
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with conn[name].cursor(row_factory=dict_row) as cur:
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cur.execute(sql)
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row = cur.fetchone()
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if row == None:
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raise Exception(sql)
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return row
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def read_all(name: str, sql: str) -> list[Row]:
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with conn[name].cursor(row_factory=dict_row) as cur:
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cur.execute(sql)
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return cur.fetchall()
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def try_read(name: str, sql: str) -> Row | None:
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with conn[name].cursor(row_factory=dict_row) as cur:
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cur.execute(sql)
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return cur.fetchone()
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def write(name: str, sql: str) -> None:
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with conn[name].cursor() as cur:
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cur.execute(sql)
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def get_current_operation(name: str) -> int:
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return int(read(name, 'select id from current_operation')['id'])
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def execute_command(name: str, command: DbChangeSet) -> ChangeSet:
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write(name, command.redo_sql)
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parent = get_current_operation(name)
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redo_sql = command.redo_sql.replace("'", "''")
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undo_sql = command.undo_sql.replace("'", "''")
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redo_cs_str = str(command.redo_cs).replace("'", "''")
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undo_cs_str = str(command.undo_cs).replace("'", "''")
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write(name, f"insert into operation (id, redo, undo, parent, redo_cs, undo_cs) values (default, '{redo_sql}', '{undo_sql}', {parent}, '{redo_cs_str}', '{undo_cs_str}')")
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current = read(name, 'select max(id) as id from operation')['id']
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write(name, f"update current_operation set id = {current}")
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return ChangeSet.from_list(command.redo_cs)
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def execute_undo(name: str, discard: bool = False) -> ChangeSet:
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row = read(name, f'select * from operation where id = {get_current_operation(name)}')
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write(name, row['undo'])
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# update foreign key
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write(name, f"update current_operation set id = {row['parent']} where id = {row['id']}")
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if discard:
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# update foreign key
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write(name, f"update operation set redo_child = null where id = {row['parent']}")
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# on delete cascade => child & snapshot
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write(name, f"delete from operation where id = {row['id']}")
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else:
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write(name, f"update operation set redo_child = {row['id']} where id = {row['parent']}")
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e = eval(row['undo_cs'])
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return ChangeSet.from_list(e)
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def execute_redo(name: str) -> ChangeSet:
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row = read(name, f'select * from operation where id = {get_current_operation(name)}')
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if row['redo_child'] == None:
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return ChangeSet()
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row = read(name, f"select * from operation where id = {row['redo_child']}")
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write(name, row['redo'])
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write(name, f"update current_operation set id = {row['id']} where id = {row['parent']}")
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e = eval(row['redo_cs'])
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return ChangeSet.from_list(e)
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def have_snapshot(name: str, tag: str) -> bool:
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return read(name, f"select id from snapshot_operation where tag = '{tag}'") != None
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def take_snapshot(name: str, tag: str) -> int | None:
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if tag == None or tag == '':
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return None
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current = get_current_operation(name)
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write(name, f"insert into snapshot_operation (id, tag) values ({current}, '{tag}')")
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return current
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def _get_parents(name: str, id: int) -> list[int]:
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ids = [id]
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while ids[-1] != 0:
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row = read(name, f'select parent from operation where id = {ids[-1]}')
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ids.append(int(row['parent']))
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return ids
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def pick_operation(name: str, operation: int, discard: bool) -> ChangeSet:
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target = operation
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curr = get_current_operation(name)
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curr_parents = _get_parents(name, curr)
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target_parents = _get_parents(name, target)
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change = ChangeSet()
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if target in curr_parents:
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for _ in range(curr_parents.index(target)):
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change.merge(execute_undo(name, discard))
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elif curr in target_parents:
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target_parents.reverse()
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curr_index = target_parents.index(curr)
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for i in range(curr_index, len(target_parents) - 1):
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write(name, f"update operation set redo_child = '{target_parents[i + 1]}' where id = '{target_parents[i]}'")
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change.merge(execute_redo(name))
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else:
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ancestor_index = -1
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while curr_parents[ancestor_index] == target_parents[ancestor_index]:
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ancestor_index -= 1
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ancestor = curr_parents[ancestor_index + 1]
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for _ in range(curr_parents.index(ancestor)):
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change.merge(execute_undo(name, discard))
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target_parents.reverse()
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curr_index = target_parents.index(ancestor)
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for i in range(curr_index, len(target_parents) - 1):
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write(name, f"update operation set redo_child = '{target_parents[i + 1]}' where id = '{target_parents[i]}'")
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change.merge(execute_redo(name))
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return change.compress()
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def pick_snapshot(name: str, tag: str, discard: bool) -> ChangeSet:
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if not have_snapshot(name, tag):
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return ChangeSet()
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target = int(read(name, f"select id from snapshot_operation where tag = '{tag}'")['id'])
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return pick_operation(name, target, discard)
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def _get_change_set(name: str, operation: int, undo: bool) -> ChangeSet:
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row = read(name, f'select * from operation where id = {operation}')
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field= 'undo_cs' if undo else 'redo_cs'
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return ChangeSet.from_list(eval(row[field]))
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def sync_with_server(name: str, operation: int) -> ChangeSet:
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fr = operation
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to = get_current_operation(name)
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fr_parents = _get_parents(name, fr)
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to_parents = _get_parents(name, to)
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change = ChangeSet()
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if fr in to_parents:
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index = to_parents.index(fr) - 1
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while index >= 0:
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change.merge(_get_change_set(name, to_parents[index], False)) #redo
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index -= 1
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elif to in fr_parents:
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index = 0
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while index <= fr_parents.index(to) - 1:
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change.merge(_get_change_set(name, fr_parents[index], True))
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index += 1
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else:
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ancestor_index = -1
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while fr_parents[ancestor_index] == to_parents[ancestor_index]:
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ancestor_index -= 1
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ancestor = fr_parents[ancestor_index + 1]
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index = 0
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while index <= fr_parents.index(ancestor) - 1:
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change.merge(_get_change_set(name, fr_parents[index], True))
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index += 1
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index = to_parents.index(ancestor) - 1
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while index >= 0:
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change.merge(_get_change_set(name, to_parents[index], False))
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index -= 1
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return change.compress()
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def get_restore_operation(name: str) -> int:
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return read(name, f'select * from restore_operation')['id']
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