RE: [sqlalchemy] m2m introspection
Thanks! Yes, it is documented, and I tried to sift through the URLs before asking, but it's kind of difficult (at least for me) to understand where exactly should I be looking for a particular piece of introspection info. From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com] On Behalf Of Michael Bayer Sent: Sunday, December 08, 2013 10:47 PM To: sqlalchemy@googlegroups.com Subject: Re: [sqlalchemy] m2m introspection with modern sqlalchemy do this: from sqlalchemy import inspect for rel in inspect(MyClass).relationships: target_class = rel.mapper.class_ this stuff is all documented, though it involves familiarizing with a few basic constructs like Mapper and RelationshipProperty: http://docs.sqlalchemy.org/en/rel_0_9/core/inspection.html?highlight=inspect #sqlalchemy.inspection http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html?highlight=relat ionships#sqlalchemy.orm.mapper.Mapper.relationships http://docs.sqlalchemy.org/en/rel_0_9/orm/internals.html#sqlalchemy.orm.prop erties.RelationshipProperty.mapper http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#sqlalchemy.orm. mapper.Mapper.class_ On Dec 8, 2013, at 5:55 AM, Alexey Vihorev viho...@gmail.com wrote: Hi again! I can do MyClass.iterate_properties()and check if a property is m2m relationship. But how can I find out which class it references? 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 mailto:sqlalchemy+unsubscr...@googlegroups.com sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to mailto:sqlalchemy@googlegroups.com sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/groups/opt_out 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. For more options, visit https://groups.google.com/groups/opt_out.
[sqlalchemy] multiple databases?
hi all, i don't know if anyone have to go through this, but here's a question: is it possible to use multiple databases sources (like postgres and mysql) in a single application? my best regards, richard. -- 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. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] multiple databases?
ok, disconsider, i may use mike's session router: http://techspot.zzzeek.org/2012/01/11/django-style-database-routers-in-sqlalchemy/ On 12/09/2013 04:08 PM, Richard Gerd Kuesters wrote: hi all, i don't know if anyone have to go through this, but here's a question: is it possible to use multiple databases sources (like postgres and mysql) in a single application? my best regards, richard. -- 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. 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. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] multiple databases?
Hi Richard There are no problems connecting to multiple database sources in the one application - we do it all the time :-) Cheers Warwick On 10 Dec 2013, at 4:08 am, Richard Gerd Kuesters rich...@humantech.com.br wrote: hi all, i don't know if anyone have to go through this, but here's a question: is it possible to use multiple databases sources (like postgres and mysql) in a single application? my best regards, richard. -- 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. 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. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Merge(load=False) woes
On Wednesday, August 25, 2010 11:02:19 AM UTC-4, Michael Bayer wrote: On Aug 25, 2010, at 10:47 AM, Michael Bayer wrote: On Aug 25, 2010, at 9:37 AM, Nikolaj wrote: Hello, I'm struggling to use the Beaker caching example in my project. Accessing any attribute on an instance from cache triggers a load from database of the instance - even trying to read the primary key! that means the instances that you're putting in the cache are expired, or at least those attributes you are attempting to read.The beaker example takes the objects from a result and sends them straight to the cache, but does not detach them from the current session. Therefore, if your backend is the memory backend, the objects in the cache are the same as those in your current session and they'll get expired when the session is committed or rolled back. There's not a really spectacular way to get around that except to not use the memory backend, use one that pickles like memcached (well, pretty much memcached is the only backend I'd ever use, but the file/dbm file backends would work here too). well, this probably would work, this diff is against tip: diff -r 568ef214c1ac examples/beaker_caching/caching_query.py --- a/examples/beaker_caching/caching_query.pyMon Aug 23 18:17:31 2010 -0400 +++ b/examples/beaker_caching/caching_query.pyWed Aug 25 10:55:53 2010 -0400 @@ -63,8 +63,15 @@ if particular attributes have been configured. + +def createfunc(): +items = list(Query.__iter__(self)) +for item in items: +self.session.expunge(item) +return items + if hasattr(self, '_cache_parameters'): -return self.get_value(createfunc=lambda: list(Query.__iter__(self))) +return self.get_value(createfunc=createfunc) else: return Query.__iter__(self) I've added a comment in the example regarding this. I want to cache mapped objects from rows which will not change during the process lifetime of a web application, so I used the memory backend. Based on the comment in the example from SQLAlchemy 0.7.9, I have also implemented this approach of caching detached objects. It mostly works fine. However, sometimes objects lazily loaded from a collection relationship and cached via RelationshipObject are still detached when the application code gets them. It looks like CachingQuery.get_value() should make sure any objects loaded from the cache are merged, but somehow that's not happening. The web application is a single-threaded, long lived process which maintains one Session object for its entire lifetime, repeatedly committing or rolling back for each HTTP request. I'm only seeing the detached objects on the request to a given process so it seems that objects loaded from the database for inserting into the cache are staying detached but those fetched from the cache on subsequent requests are properly merged. Do you have any idea why this would be or where I should investigate? -- 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. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] Merge(load=False) woes
On Dec 9, 2013, at 11:20 PM, Jonathan Rogers jonathanrrog...@gmail.com wrote: I want to cache mapped objects from rows which will not change during the process lifetime of a web application, so I used the memory backend. Based on the comment in the example from SQLAlchemy 0.7.9, I have also implemented this approach of caching detached objects. It mostly works fine. However, sometimes objects lazily loaded from a collection relationship and cached via RelationshipObject are still detached when the application code gets them. It looks like CachingQuery.get_value() should make sure any objects loaded from the cache are merged, but somehow that's not happening. the object coming out of merge() shouldn’t have anything detached associated with it - it either merges along the relationship paths, or it doesn’t and those relationships come out unloaded. is this something you can distill down to a test case ? The web application is a single-threaded, long lived process which maintains one Session object for its entire lifetime, repeatedly committing or rolling back for each HTTP request. I'm only seeing the detached objects on the request to a given process so it seems that objects loaded from the database for inserting into the cache are staying detached but those fetched from the cache on subsequent requests are properly merged. Do you have any idea why this would be or where I should investigate? -- 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 tosqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/groups/opt_out. signature.asc Description: Message signed with OpenPGP using GPGMail
Re: [sqlalchemy] Merge(load=False) woes
Michael Bayer wrote: On Dec 9, 2013, at 11:20 PM, Jonathan Rogers jonathanrrog...@gmail.com mailto:jonathanrrog...@gmail.com wrote: I want to cache mapped objects from rows which will not change during the process lifetime of a web application, so I used the memory backend. Based on the comment in the example from SQLAlchemy 0.7.9, I have also implemented this approach of caching detached objects. It mostly works fine. However, sometimes objects lazily loaded from a collection relationship and cached via RelationshipObject are still detached when the application code gets them. It looks like CachingQuery.get_value() should make sure any objects loaded from the cache are merged, but somehow that's not happening. the object coming out of merge() shouldn’t have anything detached associated with it - it either merges along the relationship paths, or it doesn’t and those relationships come out unloaded. is this something you can distill down to a test case ? Yeah, that's what I thought about merge. The behavior I've observed is intimately tied to my application so I'll try to come up with a test case based on just the Beaker caching example. -- Jonathan Rogers -- 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. For more options, visit https://groups.google.com/groups/opt_out.
[sqlalchemy] No operator matches the given name and argument filtering on postgres array
I'm trying to work with the postgres ARRAY type and I'm having a hard time
figuring out what I'm doing wrong with filtering queries on the array
column. Here's some sample code, omitting the session setup:
class MyTable(Base):
__tablename__ = 'mytable'
id = Column(Integer, primary_key=True)
myset = Column(sqlalchemy.dialects.postgresql.ARRAY(String))
Base.metadata.create_all(engine)
z = ['a', 'b', 'c']
match = session.query(MyTable).\
filter(MyTable.myset == z).\
all()
Note that the table is completely empty at this point, and has just been
created by the create_all() method. I expect to get back an empty 'match'
list, but when the query runs I get a long stack trace and the following
sql error:
sqlalchemy.exc.ProgrammingError: (ProgrammingError) operator does not
exist: character varying[] = text[]
LINE 3: WHERE mytable.myset = ARRAY[E'a', E'b', E'c']
^
HINT: No operator matches the given name and argument type(s). You might
need to add explicit type casts.
'SELECT mytable.id AS mytable_id, mytable.myset AS mytable_myset \nFROM
mytable \nWHERE mytable.myset = %(myset_1)s' {'myset_1': ['a', 'b', 'c']}
On the off chance it mattered, I've tried setting z to be a tuple instead
of a list, but no joy there either. What am I misunderstanding about how
the array type works?
Thanks!
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Re: [sqlalchemy] No operator matches the given name and argument filtering on postgres array
On Dec 10, 2013, at 12:00 AM, Matthew Pounsett matt.pouns...@gmail.com wrote: I'm trying to work with the postgres ARRAY type and I'm having a hard time figuring out what I'm doing wrong with filtering queries on the array column. Here's some sample code, omitting the session setup: class MyTable(Base): __tablename__ = 'mytable' id = Column(Integer, primary_key=True) myset = Column(sqlalchemy.dialects.postgresql.ARRAY(String)) Base.metadata.create_all(engine) z = ['a', 'b', 'c'] match = session.query(MyTable).\ filter(MyTable.myset == z).\ all() that’s a little strange but you can get around it using CAST: match = session.query(MyTable).\ filter(MyTable.myset == cast(z, ARRAY(String))).\ all() though maybe there’s a better operator to use for array == array comparison, not sure of course if you declare you column like this: myset = Column(ARRAY(Text)) it works…..in Postgresql there’s no real difference between TEXT and VARCHAR (which is unusual). Not sure why PG can’t cast between array of VARCHAR vs. TEXT but I bet there’s some info on the web about that, it’s unusual PG would have a problem with something like that (though a google seems to confirm it). signature.asc Description: Message signed with OpenPGP using GPGMail
