Re: [sqlalchemy] selecting null
On Aug 20, 2014, at 7:16 PM, Dave Vitek wrote:
> Hi all,
>
> I recently upgraded from 0.7.10 to 0.9.7. I'm seeing what looks like a
> regression:
>
> (Pdb) p str(select([null(), null()]))
> 'SELECT NULL AS anon_1'
>
> After the upgrade, sqlalchemy seems to coalesce multiple adjacent nulls into
> a single one. I can work around the problem by doing this instead:
>
> (Pdb) p str(select([literal_column('NULL'), literal_column('NULL')]))
> 'SELECT NULL, NULL'
>
> Is there a better way of doing this? Is this a bug?
>
> I'm doing this to feed an INSERT statement as in insert().from_select(...).
select()'s generally like for expressions to be named, so at the very least,
give these a label, e.g. select([null().label('n1'), null().label('n2')]).
as far as why it's doing that, sure its probably a bug
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[sqlalchemy] selecting null
Hi all,
I recently upgraded from 0.7.10 to 0.9.7. I'm seeing what looks like a
regression:
(Pdb) p str(select([null(), null()]))
'SELECT NULL AS anon_1'
After the upgrade, sqlalchemy seems to coalesce multiple adjacent nulls
into a single one. I can work around the problem by doing this instead:
(Pdb) p str(select([literal_column('NULL'), literal_column('NULL')]))
'SELECT NULL, NULL'
Is there a better way of doing this? Is this a bug?
I'm doing this to feed an INSERT statement as in insert().from_select(...).
- Dave
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[sqlalchemy] Re: How can I make a rollback in a sequence?
I did not know that thanks!
For future reference:
http://www.postgresql.org/docs/9.1/static/functions-sequence.html
Em quarta-feira, 20 de agosto de 2014 15h02min55s UTC-3, Rafael Henrique da
Silva Correia escreveu:
>
> Hi !
>
> I have a block of code similar to this I made to test:
>
> def TEST():
>> teste = Test(descricao=str('wololo'))
>>
>> try:
>> db.session.add(wololo)
>> db.session.commit()
>> db.session.close()
>> except IntegrityError, e:
>> db.session.rollback()
>> db.session.close()
>> print e.message
>>
>> sql = db.session.execute('select * from public.test_id_seq;')
>> result = sql.fetchall()
>> print "Sequence select:"
>> print result[0][0]
>> print result[0][1]
>>
>> TEST()
>>
>
> My model is:
>
> class Test(db.Model):
>> id = db.Column(db.BigInteger, db.Sequence('test_id_seq',
>> metadata=db.metadata), primary_key = True)
>> description = db.Column(db.String(50), unique=True, nullable=False)
>> def __init__(self, description):
>> self.description = description
>>
>
> I dont receive any error BUUUTT my sequence increases even in a case
> except. My database is PostgreeSQL 9.3.5 and configuration is:
>
> SQLALCHEMY_DATABASE_URI = 'postgresql://' + database_username + ':' + \
>> database_password + "@" + database_address +":" + database_port + "/" + \
>> database_name
>
>
> I created the base of my project following the official documentation
> Flask Flask-SQLAlchemy on http://flask.pocoo.org/docs/patterns/sqlalchemy/
>
> I read many many many examples on google, but none helped me ... already
> tried many things ... can anyone help me?
>
> Thank you!
>
>
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Re: [sqlalchemy] How can I make a rollback in a sequence?
> On 20 Aug 2014, at 20:02, Rafael Henrique da Silva Correia
> wrote:
>
> Hi !
>
> I have a block of code similar to this I made to test:
>
> def TEST():
> teste = Test(descricao=str('wololo'))
>
> try:
> db.session.add(wololo)
> db.session.commit()
> db.session.close()
> except IntegrityError, e:
> db.session.rollback()
> db.session.close()
> print e.message
>
> [..]
> I dont receive any error BUUUTT my sequence increases even in a case except
That’s just how PostgreSQL works. From the PostgreSQL documentation:
Important: To avoid blocking concurrent transactions that obtain numbers from
the same sequence, a nextval operation is never rolled back; that is, once a
value has been fetched it is considered used, even if the transaction that did
the nextval later aborts. This means that aborted transactions might leave
unused "holes" in the sequence of assigned values.
Wichert.
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[sqlalchemy] How can I make a rollback in a sequence?
Hi !
I have a block of code similar to this I made to test:
def TEST():
> teste = Test(descricao=str('wololo'))
>
> try:
> db.session.add(wololo)
> db.session.commit()
> db.session.close()
> except IntegrityError, e:
> db.session.rollback()
> db.session.close()
> print e.message
>
> sql = db.session.execute('select * from public.test_id_seq;')
> result = sql.fetchall()
> print "Sequence select:"
> print result[0][0]
> print result[0][1]
>
> TEST()
>
My model is:
class Test(db.Model):
> id = db.Column(db.BigInteger, db.Sequence('test_id_seq',
> metadata=db.metadata), primary_key = True)
> description = db.Column(db.String(50), unique=True, nullable=False)
> def __init__(self, description):
> self.description = description
>
I dont receive any error BUUUTT my sequence increases even in a case
except. My database is PostgreeSQL 9.3.5 and configuration is:
SQLALCHEMY_DATABASE_URI = 'postgresql://' + database_username + ':' + \
> database_password + "@" + database_address +":" + database_port + "/" + \
> database_name
I created the base of my project following the official documentation Flask
Flask-SQLAlchemy on http://flask.pocoo.org/docs/patterns/sqlalchemy/
I read many many many examples on google, but none helped me ... already
tried many things ... can anyone help me?
Thank you!
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