Re: [sqlalchemy] interaction between lazy=noload and contains_eager()
Oh, sorry, i supposed thaty contains_eager only worked for relationships,
and not for other kind of attributes :D
That's great!
Thanks!
2013/1/28 Michael Bayer mike...@zzzcomputing.com
what additional behaviors are you looking for that the @property approach
isn't giving you ? Options include turning it into a synonym() which
would allow it to be a little bit more transparent.
On Jan 28, 2013, at 4:55 AM, Pau Tallada wrote:
Hi,
Sorry to insist on this :P
But there is any way to get this kind of behaviour, the virtual
column/relationship?
Thanks!
Pau.
2013/1/24 Pau Tallada tall...@pic.es
Hi Michael,
As always, thank you very much for your dedication :)
I recognize that I am always trying to reach the edges of your wonderful
library.
That example is just a sample of what I am trying to accomplish:
Some sort of virtual column/relationship, that it is not mapped to any
column, but it can be batch-loaded in a set of instances using a
carefully-crafted contains_eager.
That way, using a descriptor, if the attribute is not in __dict__ (as you
just pointed), i can craft a CTE to fetch the attribute.
Or, if the user knows better, will use a with_transformation on top of
his query to fetch the attribute for all the queried instances.
Thank you again!
2013/1/23 Michael Bayer mike...@zzzcomputing.com
On Jan 23, 2013, at 4:28 PM, Pau Tallada wrote:
Hi,
I have prepared a sample of code to ilustrate this behaviour :)
Summarizing:
session.expunge_all()
n2 =
session.query(Node).filter_by(name='n2').options(joinedload('ancestors')).one()
print n2.ancestors
AND:
session.expunge_all()
n2 = session.query(Node).filter_by(name='n2').one()
n2 =
session.query(Node).filter_by(name='n2').options(joinedload('ancestors')).one()
print n2.ancestors
do NOT produce the same result when the collection is lazy='noload'.
In the latter, the collection is empty, even after we fetch its contents
with a joinedload.
Ah well without actually running it, I can say that the joinedload for
the second case won't have an effect like that, since n2.ancestors is
already loaded, as the effect of noload is to populate the attribute
with an empty collection (or None for a scalar). noload is not very
widely used and was sort of an added-in strategy from very early versions.
What it appears like you're looking for on anscestors is just the
default lazy loader. Above, when you load n2 without any options,
n2.anscestors will not be present in n2.__dict__ at all, and that's what
unloaded means. Hitting it again with the joinedload() should populate
the collection.
But there's not really a built in system of, don't load this mapped
attribute, but also don't load anything when touched. So if you stuck
with noload, you'd have to call expire() on ancestors first in order to
get a subsequent loader to populate it.
I guess if I really wanted an attribute like this, I'd need to wrap it
under a @property:
@property
def ancestors(self):
if _ancestors in self.__dict__:
return self._anscestors
else:
return None
if I think of a better way I'll let you know.
2013/1/23 Pau Tallada tall...@pic.es
Ok, thank you very much :D
I'll keep poking, and i'll try to provide a sample code :P
2013/1/23 Michael Bayer mike...@zzzcomputing.com
On Jan 23, 2013, at 6:49 AM, Pau Tallada wrote:
One final comment. With the contains_eager query, the instances that
are part of the collection are retrieved from the database but not stored
on the identity_map. Is that also the expected behaviour, isn't it?
I need to read your whole email more closely but on this point, that's
not true at all. Every object that the Session loads from the database
goes directly to the identity map.The identity map is weak
referencing,
so if no other references remain to a particular object, it will disappear
from the identity map also, but that implies that object is not accessible
anywhere else either.
Since it seems like you've been poking around, you might want to
continue poking around some more given that information until I have time
to look at the rest of your email.
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[sqlalchemy] Mandatory fields in tables referencing each other
Hello everybody,
I'm currently using PostgreSQL 8.4.9 and SQLAlchemy 0.7.9, and there's an
issue I just can't seem to solve.
There are 2 tables, User and People. The idea behind this is to have User's
people_id column point to that user's personal data, and People's
user_id point to the user who created that person. Neither field can be
NULL. This creates an obvious circular dependency when inserting the very
first user and its personal data, hence the use of post_update and use_alter
.
Each schema is in a separate file, so they can't import each other. These
are their structures:
class User(DeclarativeBase):
__tablename__ = 'user'
id = Column(Integer,autoincrement=True,primary_key=True)
people_id = Column(Integer, ForeignKey('people.id', use_alter=True,
name='alter_people_id'), nullable=False, unique=True)
logname = Column(Unicode(200), unique=True)
password = Column(Unicode(128))
people = relation(People, primaryjoin = People.id == people_id,
post_update=True)
class People(DeclarativeBase):
__tablename__ = people
id = Column(Integer, autoincrement=True, primary_key=True)
name = Column(Unicode(128))
[...]
user_id = Column(Integer, ForeignKey('user.id', use_alter=True,
name='alter_user_id'), nullable=False)
Here's what I'm trying to do:
user = User()
user.logname = 'sysadmin'
user.password = 'blah'
user.id = 1
user.people_id = 1
session.add(user)
ppl = People()
ppl.name = 'sysadmin'
ppl.id = 1
ppl.user_id = 1
session.add(ppl)
session.flush()
transaction.commit()
This raises an IntegrityError (insert or update on table user violates
foreign key constraint alter_people_id). I tried using
session.add_all([usr,ppl]) instead of session.add, switching the order in
which data is added to the current session, giving the use_alter attirbute
to only one of the tables, and the best I can get is a different
IntegrityError (this time on the other table, violating the other
constraint).
Thanks in advance to whoever can help me.
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[sqlalchemy] Session identity map and PyPy
Hello, I am in the process of migrating to PyPy and have a handful of unit test failing due to the different garbage collector and SQLAlchemy's usage of weak references in the Session identity map. Most failures are probably safe to ignore and all of them are fixed after manually calling gc.collect() somewhere in the test. One specific failure though looks more worrying: a Session.rollback() call in the test's tearDown() method raises InvalidRequestError: Can't attach instance `X`; another instance with key (class `X`, (8L, 1L)) is already present in this session. Before digging deeper, any idea on why it is triggered here and not in any other test? Is there another/better way to prevent it other than calling gc.collect() before Session.rollback() (and perhaps other Session operations)? More generally, are there any other known issues and caveats of running SQLAlchemy on PyPY? Thanks for any tip, George -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Problems with retroactive changes to Query objects
Hi Michael! Am Dienstag, 29. Januar 2013, 12:23:01 schrieb Michael Bayer: … it's usually going to complicate things if you mix implicit and explicit joins together. The issue should be solved if you create a clean string of joins: s.query(results1.id, results2.id).select_from(results1).join(results2, results1.foo=results2.bar).join(...).join(...) Thank you for the quick and helpful answer and the hint to select_from(); you are right that this solves my main problem (it does suffer from the same bad performance, but that's most likely a problem with my ERM). that way when you add another join to OutputParameterValue the query will not have any confusion in how to string this additional JOIN. I am still not sure if this confusion isn't a bug or weakness in SA that should be either fixed or handled with a more explicit error message. E.g. the join() could raise an error instead of silently throwing the first part of the FROM clause away. (OTOH, I don't see why the latter has to happen in the first place.) Thanks again, and have a nice day, Hans -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Docs in PDF are not being generated
the PDFS have generated very poorly for quite some time and readthedocs environment is not able to adapt to the many warnings it generates for SQLAlchemy's documentation. I've was n the Sphinx list a few years ago at this point asking for solutions regarding some of these warnings and was not able to get help on them - some of the constructs that Sphinx allows (and which we really need, namely code examples underneath a :param:) aren't compatible with their LaTeX model.I don't have the resources personally to keep banging my head against the immensely antiquated LaTeX tools, not to mention readthedocs not getting around to fixing things either, so I've taken the PDF links off the site. On Jan 30, 2013, at 2:50 AM, Vraj Mohan wrote: Hi, I noticed that documents in PDF for 0.8 and development are not being generated in readthedocs.org. I tried to build these myself with a development snapshot and had the same failures. I then noticed that if a pickled environment was already created, the PDF would be generated fine. In other words, make pickle, make html, etc would create a pickled environment which would then cause make latexpdf to succeed. I am not an expert on Sphinx - I thought this would be useful information for someone more knowledgeable than me. --Vraj Mohan -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Problems with retroactive changes to Query objects
On Jan 30, 2013, at 8:47 AM, Hans Meine wrote: I am still not sure if this confusion isn't a bug or weakness in SA that should be either fixed or handled with a more explicit error message. the usage pattern as is will likely never be feasible; SELECT * FROM A, B JOIN C on onclause, and then to say JOIN A to D onto that implies the statement would then be SELECT * FROM A JOIN D onclause, B JOIN C onclause, it's not a good practice to structure the statement like that in the first place and the Query object has enough complexity going on just to keep track of a single chain of joins. You can structure a statement like that with plain select() and join() constructs though, not sure what query planners will think of it. E.g. the join() could raise an error instead of silently throwing the first part of the FROM clause away. (OTOH, I don't see why the latter has to happen in the first place.) OK so that part I'm a little curious about as well, from what I recall I didn't quite see what aspect would be removing the A from the FROM clause as the join() you added didn't specify A as the left side in the usual way, so a short test case that is actually runnable and illustrates a working model would be of help here. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Mandatory fields in tables referencing each other
On Jan 30, 2013, at 5:00 AM, Matteo wrote:
Hello everybody,
I'm currently using PostgreSQL 8.4.9 and SQLAlchemy 0.7.9, and there's an
issue I just can't seem to solve.
There are 2 tables, User and People. The idea behind this is to have User's
people_id column point to that user's personal data, and People's user_id
point to the user who created that person. Neither field can be NULL. This
creates an obvious circular dependency when inserting the very first user and
its personal data, hence the use of post_update and use_alter.
Each schema is in a separate file, so they can't import each other. These are
their structures:
class User(DeclarativeBase):
__tablename__ = 'user'
id = Column(Integer,autoincrement=True,primary_key=True)
people_id = Column(Integer, ForeignKey('people.id', use_alter=True,
name='alter_people_id'), nullable=False, unique=True)
logname = Column(Unicode(200), unique=True)
password = Column(Unicode(128))
people = relation(People, primaryjoin = People.id == people_id,
post_update=True)
class People(DeclarativeBase):
__tablename__ = people
id = Column(Integer, autoincrement=True, primary_key=True)
name = Column(Unicode(128))
[...]
user_id = Column(Integer, ForeignKey('user.id', use_alter=True,
name='alter_user_id'), nullable=False)
both of the foreign key columns are nullable=False. this creates an impossible
situation, SQL-wise, as only one row can be added at a time. The row that goes
in first necessarily needs to have the FK column be NULL, until the second row
can go in and the UPDATE statement can set it to something.
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Re: [sqlalchemy] Session identity map and PyPy
On Jan 30, 2013, at 5:43 AM, George Sakkis wrote: Hello, I am in the process of migrating to PyPy and have a handful of unit test failing due to the different garbage collector and SQLAlchemy's usage of weak references in the Session identity map. Most failures are probably safe to ignore and all of them are fixed after manually calling gc.collect() somewhere in the test. this is true but FTR we do have a pypy suite up on jenkins.sqlalchemy.org, we don't run it often because it takes hours, but we did go through lots of effort to ensure that all the tests pass, and those that just really need cPython's GC are skipped. Unless you're referring to your own tests. One specific failure though looks more worrying: a Session.rollback() call in the test's tearDown() method raises InvalidRequestError: Can't attach instance `X`; another instance with key (class `X`, (8L, 1L)) is already present in this session. Before digging deeper, any idea on why it is triggered here and not in any other test? it would be impossible to say without specific details and examples. Generally there is probably some logic that relies upon an X(8, 1) being garbage collected from the Session (note the identity map is weak referencing) so that an add() later on can succeed. An add() inside of a tearDown() is kind of strange, though, the stack trace would tell you how it's getting there. Is there another/better way to prevent it other than calling gc.collect() before Session.rollback() (and perhaps other Session operations)? I'd make sure the tests use a brand new Session for every test that's clean. More generally, are there any other known issues and caveats of running SQLAlchemy on PyPY? Our own test suite has a lot of performance issues with Pypy, not sure if due to memory or JIT crunching or what, I reported it to their bug tracker at the request of their developers. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Docs in PDF are not being generated
Is there any interest in having this fixed? I am new to SQLAlchemy and am keen to learn both SQLAlchemy and Sphinx, and have some time to spare. If there's not much interest in the PDFs, I am open to help in other areas. --Vraj On Wed, Jan 30, 2013 at 9:41 AM, Michael Bayer mike...@zzzcomputing.com wrote: the PDFS have generated very poorly for quite some time and readthedocs environment is not able to adapt to the many warnings it generates for SQLAlchemy's documentation. I've was n the Sphinx list a few years ago at this point asking for solutions regarding some of these warnings and was not able to get help on them - some of the constructs that Sphinx allows (and which we really need, namely code examples underneath a :param:) aren't compatible with their LaTeX model.I don't have the resources personally to keep banging my head against the immensely antiquated LaTeX tools, not to mention readthedocs not getting around to fixing things either, so I've taken the PDF links off the site. On Jan 30, 2013, at 2:50 AM, Vraj Mohan wrote: Hi, I noticed that documents in PDF for 0.8 and development are not being generated in readthedocs.org. I tried to build these myself with a development snapshot and had the same failures. I then noticed that if a pickled environment was already created, the PDF would be generated fine. In other words, make pickle, make html, etc would create a pickled environment which would then cause make latexpdf to succeed. I am not an expert on Sphinx - I thought this would be useful information for someone more knowledgeable than me. --Vraj Mohan -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Mandatory fields in tables referencing each other
Alright, many thanks. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Docs in PDF are not being generated
On 30/01/2013 17:53, Michael Bayer wrote: On Jan 30, 2013, at 10:10 AM, Vraj Mohan wrote: Is there any interest in having this fixed? I'd love someone to take it on and fix it, sure.I've been asking around for help for years, as I still see people publishing entire books with LaTeX. What about rst2pdf instead of going via LaTex? http://techtonik.rainforce.org/2010/05/sphinx-pdf-with-rst2pdf.html I used on smallish docs, so don't know how it will do with SQLAlchemy. Werner -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Docs in PDF are not being generated
Keep in mind were ideally working with readthedocs standard tools. It really should be possible for this to all work using standard approaches. Sent from my iPhone On Jan 30, 2013, at 12:50 PM, Werner werner.bru...@sfr.fr wrote: On 30/01/2013 17:53, Michael Bayer wrote: On Jan 30, 2013, at 10:10 AM, Vraj Mohan wrote: Is there any interest in having this fixed? I'd love someone to take it on and fix it, sure.I've been asking around for help for years, as I still see people publishing entire books with LaTeX. What about rst2pdf instead of going via LaTex? http://techtonik.rainforce.org/2010/05/sphinx-pdf-with-rst2pdf.html I used on smallish docs, so don't know how it will do with SQLAlchemy. Werner -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Docs in PDF are not being generated
On Jan 30, 2013, at 17:53 , Michael Bayer mike...@zzzcomputing.com wrote: I've asked people before about this seemingly ridiculous generate twice requirement of LaTeX and I get these incredulous answers like why? what's wrong with running it twice?, as though I'm being unreasonable. It is an artefact if how TeX works: it makes a single pass over your document, so if it is missing something that is defined later, like TOC entries, it can't fill them in and skips them. It does write status files during processing so that a later run will have the missing information. In some case you may even need to run it more than two times to get page number references to stabilise. This strategy was probably an excellent choice in the late 70s / early 80s when TeX was created and memory was a scarce resource. Wichert. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Docs in PDF are not being generated
Standardization is always necessary, just a question, which tool would you suggest for converting things to PDF? Sent from my iBath On Jan 30, 2013, at 20:16, Michael Bayer mike...@zzzcomputing.com wrote: Keep in mind were ideally working with readthedocs standard tools. It really should be possible for this to all work using standard approaches. Sent from my iPhone On Jan 30, 2013, at 12:50 PM, Werner werner.bru...@sfr.fr wrote: On 30/01/2013 17:53, Michael Bayer wrote: On Jan 30, 2013, at 10:10 AM, Vraj Mohan wrote: Is there any interest in having this fixed? I'd love someone to take it on and fix it, sure.I've been asking around for help for years, as I still see people publishing entire books with LaTeX. What about rst2pdf instead of going via LaTex? http://techtonik.rainforce.org/2010/05/sphinx-pdf-with-rst2pdf.html I used on smallish docs, so don't know how it will do with SQLAlchemy. Werner -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
[sqlalchemy] Tracking changes made to mapped objects
I'm using Sqlalchemy for the first time and am slowly figuring out most of what I need. However there is one aspect I would like some advice about. I have a GUI program that gets some number of items (say data about movies for example) from a database and lets the user edit them including foreign key linked table data like directors or actors. My question is how to track changes. A user may change some attribute of a movie (or of one of the subtables linked to it), say the year made, then page to a different movie, and change something there. Such changes are reflected in the session.dirty, session.new and session.deleted properties for a while (up to some point where Sqlalchemy decides it needs to do a flush). But after a flush, the .dirty (et.al.) properties no longer show anything but the changes are still not permanent since no commit has been done yet. I need to indicate in the GUI *what* mapped objects and what attributes of those objects have been changed, perhaps by displaying values in red (for example) to allow the user to review or revert changes before saving (i.e. committing). How can I determine what has been changed, even after a flush? (Or should I disable autoflushing?) How to revert some changes (but not all; for that I would just do a rollback, yes?) -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
[sqlalchemy] joinedload on inherited class causing subquery instead of raw joins?
I have a user object, and an extended user object which inherits from the
base user object. I also have a test object, which has a FK to the extended
user object. When I try this:
res = session.query(Test) \
.options(joinedload('user')) \
.all()
I see this sql generated:
SELECT test.id AS test_id, test.user_id AS test_user_id,
anon_1.users_ext_id AS anon_1_users_ext_id, anon_1.users_id AS
anon_1_users_id
FROM test LEFT OUTER JOIN (SELECT users.id AS users_id, users_ext.id AS
users_ext_id
FROM users JOIN users_ext ON users.id = users_ext.id) AS anon_1 ON
anon_1.users_ext_id = test.user_id
there are no limits or constraints on the subquery, so this takes a
nightmarish amount of time to resolve (hundreds of thousands of users in
the table), while the query i was expecting works instantly. The query I am
trying to achieve is:
SELECT test.id AS test_id, test.user_id AS test_user_id,
anon_1.users_ext_id AS anon_1_users_ext_id, anon_1.users_id AS
anon_1_users_id
FROM test
LEFT OUTER JOIN users_ext ON users_ext.id = test.user_id
JOIN users ON users_ext.id = users.id
How can I generate the second query instead of the first? It seems like all
the parts are there, but put together in a terrible way that ensures it
will take the maximum amount of time to resolve.
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from sqlalchemy import *
from sqlalchemy.orm import relation, joinedload, create_session
from sqlalchemy.ext.declarative import declarative_base
e = create_engine('sqlite:tmp/foo.db', echo=True)
Base = declarative_base(bind=e)
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
class UserExtension(User):
__tablename__ = 'users_ext'
id = Column(Integer, ForeignKey(User.id), primary_key=True)
class Test(Base):
__tablename__ = 'test'
id = Column(Integer, primary_key=True)
user_id = Column(Integer, ForeignKey(UserExtension.id))
user = relation(UserExtension, lazy=True)
Base.metadata.drop_all()
Base.metadata.create_all()
session = create_session(bind=e)
res = session.query(Test) \
.options(joinedload('user')) \
.all()
SELECT test.id AS test_id, test.user_id AS test_user_id, anon_1.users_ext_id AS anon_1_users_ext_id, anon_1.users_id AS anon_1_users_id
FROM test LEFT OUTER JOIN (SELECT users.id AS users_id, users_ext.id AS users_ext_id
FROM users JOIN users_ext ON users.id = users_ext.id) AS anon_1 ON anon_1.users_ext_id = test.user_id
