Re: [Pypgsql-users] strange pypgsql return value

[Gerhard <ger...@gm...>]

Le 17/01/02 à 17:21, Tom Jenkins écrivit:
> hello all,
> we're migrating away from pygresql and i'm evaluating pypgsql along with
> psycopg. i found something troubling with both adapters.  when we
> execute a select of this form:
>   select count(myfield) from mytable where mykey = myvalue
> and there aren't any rows that match then we get a TypeError exception
> (psycopg returns ((None,)) which is almost as bad <wink>).  Similarly i
> was getting the same exception on sums.  Now i expected and got in
> pygresql a return of ((0,)).
> 
> is anyone else seeing this or i am missing something here

I tried to reproduce what you're describing:

Script started on Fri Jan 18 00:00:14 2002
gerhard@lilith:~$ psql -h gargamel gerhard
Welcome to psql, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help on internal slash commands
       \g or terminate with semicolon to execute query
       \q to quit

gerhard=# create table test(id serial, name varchar(20));
NOTICE:  CREATE TABLE will create implicit sequence 'test_id_seq' for SERIAL column 'test.id'
NOTICE:  CREATE TABLE/UNIQUE will create implicit index 'test_id_key' for table 'test'
CREATE
gerhard=# insert into test(name) values ('bla');
INSERT 18794 1
gerhard=# select * from test;
 id | name 
----+------
  1 | bla
(1 row)

gerhard=# select count(id), sum(id) from test where id=3245;
 count | sum 
-------+-----
     0 |    
(1 row)

gerhard=# \q
gerhard@lilith:~$ python2.1
Python 2.1.1+ (#1, Jan  8 2002, 00:37:12) 
[GCC 2.95.4 20011006 (Debian prerelease)] on linux2
Type "copyright", "credits" or "license" for more information.
>>> from pyPgSQL import PgSQL
>>> import psycopg
>>> db = PgSQL.connect(host="gargamel")
>>> cursor=db.cursor()
>>> cursor.execute("select count(id) from test where id=456")
>>> print cursor.fetchall()
[[0]]
>>> db = psycopg.connect("host=gargamel")
>>> cursor = db.cursor()
>>> cursor.execute("select count(id) from test where id=456")
>>> print cursor.fetchall()
[(0,)]
>>> 
gerhard@lilith:~$ exit

Script done on Fri Jan 18 00:05:06 2002

I was using PostgreSQL 7.1.3 and the latest released versions of pyPgSQL
and psycopg, but couldn't reproduce the problem you were describing.
Could you try to produce a testcase (SQL schema and Python code) and
upload it to the Sourceforge bug tracker or post it here?

Or perhaps I didn't understand your question correctly!?

Gerhard
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reduce(lambda x,y:x+y,map(lambda x:chr(ord(x)^42),tuple('zS^BED\nX_FOY\x0b')))