获取插入psycopg2中的多行的ID [英] getting ids of multiple rows inserted in psycopg2
问题描述
我想使用psycopg2来 INSERT
多行,然后返回所有 id
(按顺序)使用单个查询。这就是PostgreSQL的 RETURNING
扩展名设计的,并且使用 cursor.execute
似乎可以正常工作:
cursor.execute(
INSERT INTO my_table(field_1,field_2)
VALUES(0,0) ,(0,0)返回id;
)
打印cursor.fetchall()
[(1,),(2,)]
现在,为了传递动态生成的数据,似乎是 cursor.executemany
是方法:
data = [(0,0),(0,0)]
cursor.executemany(
INSERT INTO my_table(field_1,field_2)
VALUES(%s,%s)RETURNING id;,
数据
)
但是,在这种情况下, cursor.fetchall()
产生以下内容:
[(4,),(None,)]
如何正确返回所有 id
您不应该能够从 executemany
获得结果:
该功能对于更新数据库的命令最有用:查询返回的任何结果集都将被丢弃。
Per psycopg2文档。
最好是在事务中循环单个 insert
,或使用多值 insert ...返回
,尽管在后一种情况下,您必须小心使用另一个输入值来匹配返回的ID,但不能仅仅假设返回的ID的顺序与输入的 VALUES
列表。
当我在本地运行测试时,它只是失败了:
>>>导入psycopg2
>> conn = psycopg2.connect( dbname = regress)
>> curs = conn.cursor()
>> curs.execute(创建表my_table(id串行主键,field_1整数,field_2整数);)
>> data = [(0,0),(0,0)]
>> curs.executemany(
... INSERT INTO my_table(field_1,field_2)
... VALUES(%s,%s)RETURNING id;,
...数据
...)
>>
>> curs.fetchall()
追溯(最近一次调用为最后一次):
文件< stdin>,在< module>中的第1行。
psycopg2.ProgrammingError:无结果可获取
经psycopg2 2.5.1。测试。
I'd like to use psycopg2 to INSERT
multiple rows and then return all the id
s (in order) using a single query. This is what PostgreSQL's RETURNING
extension is designed for, and it seems to work fine using cursor.execute
:
cursor.execute(
"INSERT INTO my_table (field_1, field_2) "
"VALUES (0, 0), (0, 0) RETURNING id;"
)
print cursor.fetchall()
[(1,), (2,)]
Now, in order to pass in dynamically-generated data, it seems like cursor.executemany
is the way to go:
data = [(0, 0), (0, 0)]
cursor.executemany(
"INSERT INTO my_table (field_1, field_2) "
"VALUES (%s, %s) RETURNING id;",
data
)
However, in that case, cursor.fetchall()
produces the following:
[(4,), (None,)]
How do I get it to correctly return all the id
s instead of just the one?
You're not supposed to be able to get results from executemany
:
The function is mostly useful for commands that update the database: any result set returned by the query is discarded.
Per the psycopg2 docs.
You'll be better off looping over a single insert
within a transaction, or using a multi-valued insert... returning
, though in the latter case you must be careful to match returned IDs using another input value, you can't just assume the order of returned IDs is the same as the input VALUES
list.
When I run your test locally, it simply fails:
>>> import psycopg2
>>> conn = psycopg2.connect("dbname=regress")
>>> curs = conn.cursor()
>>> curs.execute("create table my_table(id serial primary key, field_1 integer, field_2 integer);")
>>> data = [(0, 0), (0, 0)]
>>> curs.executemany(
... "INSERT INTO my_table (field_1, field_2) "
... "VALUES (%s, %s) RETURNING id;",
... data
... )
>>>
>>> curs.fetchall()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
psycopg2.ProgrammingError: no results to fetch
Tested with psycopg2 2.5.1.
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