sqlalchemy Google Group

The problem with Oldest transaction (Firebird)

a.zhabotins...@gmail.com (graf) — Tue, 18 Jun 2013 22:09:40 UT

I use SQLAlchemy inside Tornado, and I use a singleton to make the Firebird
connection inside application.
class FirebirdDatabase(object):
def __init__(self, firebird_params, echo=False):
engine =
create_engine('firebird+fdb:// %(user)s:%(password)s@%(host)s :%(port)s/%(path)s'
% firebird_params,

Re: The problem with the update

witold.g...@gmail.com (Witold Greń) — Tue, 18 Jun 2013 21:55:54 UT

This is an interesting question :)
Description: Looking for a project in which students (ManyToMany) to
address (OneToOne) with the street dying text "Jana" and delete this row.
subq =
session.query(Addressess.id).f ilter(Addressess.street.like(' %Jana%')).subquery()
session.query(Projects).filter (Projects.students.any(Person. addressess_id.in_(subq))).dele te(synchronize_session='fetch' )

Re: The problem with the update

witold.g...@gmail.com (Witold Greń) — Tue, 18 Jun 2013 21:14:51 UT

Resolverd no. 5:
session.query(Projects).filter (Projects.students.any(and_(Pe rson.gender ==
False, Person.name.like('M%') )))\
.update({Projects.name: u'New project name', Projects.supervisor_id:
1}, synchronize_session=False)
Again many thanks Michael :)

Re: [sqlalchemy] The problem with the update

mike...@zzzcomputing.com (Michael Bayer) — Tue, 18 Jun 2013 21:08:23 UT

any() does the subquery correlated to the related table for you:

s.query(Projects).filter(Proje cts.students.any(and_(Person.g ender == False, Person.name.like('x')))).count ()

Re: The problem with the update

witold.g...@gmail.com (Witold Greń) — Tue, 18 Jun 2013 20:46:29 UT

Thanks for your help Michael :)

Resolved:
No.2

subq = session.query(Person.group_lea der_id).filter(or_(Person.name ==
'Jan', Person.surname == 'Nowak')).subquery()

session.query(Person).filter(P erson.id.in_(subq)).update({Pe rson.name:
u'Łukasz'}, synchronize_session=False)

Re: [sqlalchemy] The problem with the update

mike...@zzzcomputing.com (Michael Bayer) — Tue, 18 Jun 2013 19:13:50 UT

if the database you're using doesn't support UPDATE..FROM (which is likely), the normal way is to UPDATE with a subquery, which may be correlated or in a simple case like this just using IN:

UPDATE price SET extra=20000 WHERE price.id in (select price_id from person where name like 'J%')

subq = session.query(Person.price_id) .where(Person.name.like('J%')) .subquery()

Re: [sqlalchemy] between .one() and .first()

ianmarcinkow...@gmail.com (ian marcinkowski) — Tue, 18 Jun 2013 18:30:04 UT

From the docs:
"one()

Return exactly one result or raise an exception.

Raises sqlalchemy.orm.exc.NoResultFou nd if the query selects no rows.

Raises sqlalchemy.orm.exc.MultipleRes ultsFound if multiple object
identities are returned, or if multiple rows are returned for a query
that does not return object identities."

Re: The problem with the update

witold.g...@gmail.com (Witold Greń) — Tue, 18 Jun 2013 18:01:22 UT

I try resolved problem used this code:

No 5:

sql = session.query(Projects).join(P erson,
Projects.students).filter(Pers on.gender==False, Person.name.like('M%'))

for projects in sql:
projects.supervisor_id = 1

session.commit()

but it is probably not a very efficient way?

Re: [sqlalchemy] sqlite in memory

rich...@humantech.com.br (Richard Gerd Kuesters) — Mon, 17 Jun 2013 19:29:50 UT

Petr, just found something intesting that may work for anyone:

[link]

I was able do create a database totally in memory and them just "dump"
it to a file. The process now takes about 5 minutes, against one hour+
that it took earlier.

The problem with the update

witold.g...@gmail.com (Witold Greń) — Mon, 17 Jun 2013 19:09:18 UT

Hi, I'm Witold and learn Sqlalchemy :)
I have a little problem, here it is:

This is my DB:

class Addressess(Base):

__tablename__ = 'addressess'

id = Column('id', Integer, Sequence('address_id_seq'),
primary_key=True, index=True, unique=True, nullable=False)
street = Column('street', String(200))

Re: [sqlalchemy] between .one() and .first()

encu...@gmail.com (Petr Viktorin) — Mon, 17 Jun 2013 17:57:26 UT

Simply handling NoResultFound should work just fine...

def zero_or_one(query):
try:
return query.one()
except NoResultFound:
return None

Re: [sqlalchemy] between .one() and .first()

charlie.cl...@clark-consulting.eu (Charlie Clark) — Mon, 17 Jun 2013 17:47:56 UT

Am 17.06.2013, 08:58 Uhr, schrieb Chris Withers <ch...@simplistix.co.uk>:

.count() would seem to be your friend here, at least in case that a lot of
rows might be returned.

Only if you can express that need as a query.

Charlie
--
Charlie Clark
Managing Director
Clark Consulting & Research

Re: [sqlalchemy] Unique constraints disappearing

mike...@zzzcomputing.com (Michael Bayer) — Mon, 17 Jun 2013 16:39:25 UT

unique constraints are not currently reflected. This feature was just added in master and is currently set for release in 0.9.0.

Re: [sqlalchemy] SQLAlchemy 0.8.1 + fdb, row size

mike...@zzzcomputing.com (Michael Bayer) — Mon, 17 Jun 2013 16:38:24 UT

this would be a difference in how they handle unicode. I've run tests for fdb here against unicode values and haven't observed that issue.

its possible fdb is doing the right thing here. You should carefully look at how non-ASCII characters are being placed in that column both with kinterbasdb and with fdb.

Re: [sqlalchemy] sqlite in memory

rich...@humantech.com.br (Richard Gerd Kuesters) — Mon, 17 Jun 2013 16:37:01 UT

Hmmm, never knew of that. All my "constraints" are already predefined
and inserts are in order so I won't get a broken FK. I'll try that too
see if it increases the speed (decreasing my headaches per build, lol).

Thanks a lot, Petr!