The following short script behaves differently if run with no arguments or with
arguments:
from elixir import *
import os
from sqlalchemy import Unicode, select, and_, __version__
import sys
class School(Entity):
name = Field(Unicode(50), required=True)
class Subject(Entity):
name = Field(Unicode(50), required=True)
teachers = ManyToMany('Teacher',
local_colname='course_id',
remote_colname='prof_id')
school = ManyToOne('School')
class Teacher(Entity):
name = Field(Unicode(50), required=True)
def main():
if os.path.exists('/tmp/schools.db'):
os.remove('/tmp/schools.db')
metadata.bind = "sqlite:////tmp/schools.db"
setup_all(create_tables=True)
school = School(name='Rydell High')
session.commit()
r = Subject._descriptor.find_relationship('teachers')
t = r.table
if len(sys.argv) > 1:
c = Subject.school == school
else:
c = Subject.school_id == school.id
s = select([Teacher.name],
and_(c, t.c.prof_id == Teacher.id, t.c.course_id == Subject.id))
metadata.bind.echo = True
print('Executing query using SQLAlchemy', __version__)
session.execute(s)
if __name__ == '__main__':
main()
The script chooses between two comparator conditions:
Subject.school == school
or
Subject.school_id == school.id
before running a SQLA select query using the chosen comparator. In one case the
generated SQL is printed, and in the other it's not, despite echo being set to
True. In the real program of which this is a cut-down example, the query ran
correctly in either case, so it's just the engine.echo behaviour which is odd.
Sorry this is an Elixir script - I'm unable to reproduce using just SQLAlchemy,
but it seems unlikely to be an Elixir issue. It seems to be a subtle enough bug
(if bug it is) that removing Elixir from the picture causes the bug to disappear
from view.
Why should the two cases behave differently?
Regards,
Vinay Sajip
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