我知道executemany可以用来方便地将新条目添加到数据库中;与for循环中的单个执行相比,减少
Python方法调用开销很有用.但是,我想知道这是否适用于SQLite的UPDATE.
更具体地说,请考虑以下设置:
cnx = sqlite3.connect(DATABASE) c = cnx.cursor() for path in paths: for data in some_computation(path): c.execute("UPDATE TABLENAME SET cont=? WHERE id=?",(data[1],data[0])) cnx.commit() cnx.close()
我甚至不确定下面的方法是否会更快(必须对它进行基准测试),但问题是它不起作用,因为我做错了我假设.有关在下面的代码片段中使用executemany来完成我上面发布的任务的提示吗?
cnx = sqlite3.connect(DATABASE) c = cnx.cursor() for path in paths: data_ids,data_conts = [],[] for data in some_computation(path): if len(data_ids) >= CHUNKSIZE: c.executemany("UPDATE TABLENAME SET cont=? WHERE id=?",(data_conts,data_ids)) cnx.commit() data_ids,[] data_ids.append(data[0]) data_conts.append(data[1]) c.executemany("UPDATE TABLENAME SET cont=? WHERE id=?",data_ids)) cnx.commit() cnx.commit() cnx.close()
非常感谢您的提示和见解!
编辑1:
底部示例的问题:
ProgrammingError: Incorrect number of bindings supplied. The current statement uses 2,and there are 50000 supplied.
(其中CHUNKSIZE = 50000)
编辑2:
发生同样的错误
cnx = sqlite3.connect(DATABASE) c = cnx.cursor() for path in paths: data_conts = [] for data in some_computation(path): if len(data_ids) >= CHUNKSIZE: c.executemany("UPDATE TABLENAME SET cont=? WHERE id=?",)) cnx.commit() data_conts = [] data_conts.append([data[1],data[0]]) c.executemany("UPDATE TABLENAME SET cont=? WHERE id=?",)) cnx.commit() cnx.commit() cnx.close()
但感谢@falsetru我注意到我的错误,应该是
... WHERE id=?",data_conts)
并不是
... WHERE id=?",))
解决方法
你需要传递一系列序列([[cont,id],[cont,…],而不是[cont,cont,[id,id,ID,..]):
for path in paths: params = [] for data in some_computation(path): if len(data_ids) >= CHUNKSIZE: c.executemany("UPDATE TABLENAME SET cont=? WHERE id=?",params) cnx.commit() params = [] params.append([data[1],data[0]]) if params: c.executemany("UPDATE TABLENAME SET cont=? WHERE id=?",params) cnx.commit()