On 09/06/2016 04:31 PM, Duke Dougal wrote:
I'm sorry sqlalchemy hasn't fully clicked for me yet. I'm still stuck on
this.
A I meant to be translating the sql that Michael has suggested into an
ORM query?
We're going to use the form illustrated at
http://docs.sqlalchemy.org/en/latest/core/defaults.html#context-sensitive-default-functions,
except we'll invoke a SQL statement. The example there is a little
scant and does not illustrate other common members of the "context",
that should be fixed.
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
def new_sequence(context):
return context.connection.scalar(
select([func.coalesce(func.max(Issues.sequence_number), 0) + 1]).
where(Issues.thread_id == context.current_parameters['thread_id'])
)
class Issues(Base):
__tablename__ = 'issues'
id = Column(String, primary_key=True)
thread_id = Column(Integer, nullable=False)
sequence_number = Column(Integer, unique=True, default=new_sequence)
e = create_engine("postgresql://scott:tiger@localhost/test", echo=True)
Base.metadata.create_all(e)
s = Session(e)
s.add(Issues(id='issue1', thread_id=1))
s.commit()
s.add(Issues(id='issue2', thread_id=1))
s.commit()
print(s.query(Issues.thread_id, Issues.sequence_number).all())
This is as far as I have got which results in :
NameError: name 'Issues' is not defined
Even then I still don't see how to get the "where" clause into the select.
from sqlalchemy import Column, String, Integer, DateTime, Boolean
from db_global import db
from sqlalchemy.sql import func, select
class Issues(db.Base):
__tablename__ = 'issues'
id = Column(String, primary_key=True)
thread_id = Column(String, nullable=False)
sequence_number = Column(Integer,
default=select([func.coalesce(func.max(Issues.sequence_number) + 1, 1)]))
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