Re: [sqlalchemy] bug in sqllite dialect?
Michael Bayer wrote: Has anyone (hi, list, talking to you too!) already done a custom type for this specific problem? people do custom types for all sorts of things. In the case of the Decimal here I'd likely subclass sqlalchemy.databases.sqlite.SLNumeric which should ensure that your own bind_processor() and result_processor() methods can be called. Okay, but how do I make sure this is only used when sqlite this the engine? Chris -- Simplistix - Content Management, Batch Processing Python Consulting - http://www.simplistix.co.uk -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] case sensitive Unicode and String columns
Michael Bayer wrote: How do I do this? I think all databases that SQLAlchemy supports (in fact, likely all databases in use today) support case-sensitive strings by default, so I don't know if this something you'll need to worry about in your code. Maybe I am misunderstanding what you are trying to do? hes likely referring to case-sensitive collation support. Build a TypeDecorator and intercept the dialect in the process_bind_param() method. This sounds pretty heavyweight unless I'm misunderstanding... I was hoping for something like: class MyModel(Base): __tablename__ = 'foo' ... myfield = Column(String(50,case_sensitive=True)) I know this doesn't exist, but I was hoping either it was easy to implement or a field type could be created that did the right thing no matter what the back end was... Chris -- Simplistix - Content Management, Batch Processing Python Consulting - http://www.simplistix.co.uk -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] Re: [PROPOSE] Integrate migration support in SQLAlchemy
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Lele Gaifax ha scritto: Manlio Perillo manlio.peri...@gmail.com writes: Michael Bayer ha scritto: Similarly, the concept of a version as an integer number is not really flexible enough - The idea was to keep it simple. IMHE, there's no such a beast! I would like to investigate the creation of migration scripts between branches as well. The version can then be a string, but it needs to sortable (see setuptool as an example). The mechanism of schema versioning is not at all something that belongs in SQLAlchemy core. I'm all with Michael here. Sure, for *very* simple projects, it'd be nice to have a mechanism that spits out the needed statements, but at least in my experience (going from very little to moderately big and complex schemas), maintaining an upgradable path is something better done at another level. Some steps needs an hand-crafted solution, that maybe involve dropping/recreating dependencies, temporary data-space to upgrade existing contents and so on. I think you have misunderstod my propose. The propose was not to to spits out the needed statements, but to call user defined functions for a migration path from version x to version y. That's why it should be kept simple: different users need different features, and this is up to high level applications that are built on top of the base support to migration. You can have very simple upgrade functions that use SQLAlchemy builtin DDL, or you can have complex scripts with hand written SQL. I'm interested in a reusable core. The more is simple, the more is reusable (unless it is too simple, and thus useless) [...] Regards Manlio -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkuQ/UMACgkQscQJ24LbaUSxxwCePPm9N6e+oZAqf/Zwo/kt5f9M cOsAn2UzpxfSmg3W+lOWuWADds60D/Xs =B6HL -END PGP SIGNATURE- -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] Re: Getting access to the object being updated inside a default callable?
Sorry to bug… I imagine there is no way of doing this, but would be good to know for sure. If not, this would be really useful functionality. For instance, I might want to populate one column based on the contents of one of more other columns. On 12 Jan, 11:21, Oliver Beattie oli...@obeattie.com wrote: Hi there, I feel like I'm perhaps missing something, but I wonder if there's any way to access the object being updated inside a ColumnDefault? More specifically, if I have a… let's call it DBObject (using declarative) which has a callable as its default, is there any way to access that DBObject instance inside the default function? I see it gets passed an ExecutionContext instance, but I don't see a way to get the object from there :\ If there's a way to do this, it would help me a lot :) Thanks, Oliver -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] three primary keys on association object
Hello, I have an association object declaratively with three primary keys, but on insert, the first (id) is not autoincremented. Please see test the code below from sqlalchemy import create_engine, Column,Integer, String, ForeignKey from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker,relation, backref engine = create_engine(sqlite:///:memory:,echo=False) Base=declarative_base() class Child(Base): __tablename__=Child id=Column(Integer,primary_key=True) class Association(Base): __tablename__=Association id=Column(Integer,primary_key=True) parent_id=Column(Integer,ForeignKey(Parent.id),primary_key=True) child_id=Column(Integer,ForeignKey(Child.id),primary_key=True) child=relation(Child,backref=parents) data=Column(String(32)) def __init__(self): self.data=some text class Parent(Base): __tablename__=Parent id=Column(Integer, primary_key=True) children=relation(Association,backref=backref(parent)) Base.metadata.create_all(engine) Session=sessionmaker(bind=engine) session = Session() p=Parent() a=Association() a.child=Child() p.children.append(a) session.add(p) session.query(Parent).all() I need the id for another 1:n realtion with the association object. What am I missing here? Thanks Sebastian -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] bug in sqllite dialect?
Chris Withers wrote: Michael Bayer wrote: Has anyone (hi, list, talking to you too!) already done a custom type for this specific problem? people do custom types for all sorts of things. In the case of the Decimal here I'd likely subclass sqlalchemy.databases.sqlite.SLNumeric which should ensure that your own bind_processor() and result_processor() methods can be called. Okay, but how do I make sure this is only used when sqlite this the engine? You can use a TypeDecorator to switch between implementations. I had a plan to add a pre-fab type for this to core that allows easy switching of implementations. Chris -- Simplistix - Content Management, Batch Processing Python Consulting - http://www.simplistix.co.uk -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] case sensitive Unicode and String columns
Chris Withers wrote: Michael Bayer wrote: How do I do this? I think all databases that SQLAlchemy supports (in fact, likely all databases in use today) support case-sensitive strings by default, so I don't know if this something you'll need to worry about in your code. Maybe I am misunderstanding what you are trying to do? hes likely referring to case-sensitive collation support. Build a TypeDecorator and intercept the dialect in the process_bind_param() method. This sounds pretty heavyweight unless I'm misunderstanding... I was hoping for something like: class MyModel(Base): __tablename__ = 'foo' ... myfield = Column(String(50,case_sensitive=True)) I know this doesn't exist, but I was hoping either it was easy to implement or a field type could be created that did the right thing no matter what the back end was... the MySQL string types support MySQL's collation flags so you can get close to it for at least that platform. But then you aren't platform independent. Not sure why you're so averse to creating types. The interface could not be simpler. When i used Hibernate, there was no option - you had to make types for pretty much anything non-trivial (like oracle BLOBs and such). Chris -- Simplistix - Content Management, Batch Processing Python Consulting - http://www.simplistix.co.uk -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] Re: Getting access to the object being updated inside a default callable?
Oliver Beattie wrote: Sorry to bug… I imagine there is no way of doing this, but would be good to know for sure. If not, this would be really useful functionality. For instance, I might want to populate one column based on the contents of one of more other columns. On 12 Jan, 11:21, Oliver Beattie oli...@obeattie.com wrote: Hi there, I feel like I'm perhaps missing something, but I wonder if there's any way to access the object being updated inside a ColumnDefault? More specifically, if I have a… let's call it DBObject (using declarative) which has a callable as its default, is there any way to access that DBObject instance inside the default function? I see it gets passed an ExecutionContext instance, but I don't see a way to get the object from there :\ If there's a way to do this, it would help me a lot :) The executioncontext has all the parameters for the whole statement, you can use those. But the ORM object is not available at that level. You might want to use MapperExtension.before_insert() if you need ORM-level awareness. Thanks, Oliver -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] three primary keys on association object
Sebastian Elsner wrote: Hello, I have an association object declaratively with three primary keys, but on insert, the first (id) is not autoincremented. Please see test the code below known sqlite limitation, described at http://www.sqlalchemy.org/docs/reference/dialects/sqlite.html?highlight=sqlite#auto-incrementing-beahvior from sqlalchemy import create_engine, Column,Integer, String, ForeignKey from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker,relation, backref engine = create_engine(sqlite:///:memory:,echo=False) Base=declarative_base() class Child(Base): __tablename__=Child id=Column(Integer,primary_key=True) class Association(Base): __tablename__=Association id=Column(Integer,primary_key=True) parent_id=Column(Integer,ForeignKey(Parent.id),primary_key=True) child_id=Column(Integer,ForeignKey(Child.id),primary_key=True) child=relation(Child,backref=parents) data=Column(String(32)) def __init__(self): self.data=some text class Parent(Base): __tablename__=Parent id=Column(Integer, primary_key=True) children=relation(Association,backref=backref(parent)) Base.metadata.create_all(engine) Session=sessionmaker(bind=engine) session = Session() p=Parent() a=Association() a.child=Child() p.children.append(a) session.add(p) session.query(Parent).all() I need the id for another 1:n realtion with the association object. What am I missing here? Thanks Sebastian -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] three primary keys on association object
Michael Bayer wrote: Sebastian Elsner wrote: Hello, I have an association object declaratively with three primary keys, but on insert, the first (id) is not autoincremented. Please see test the code below known sqlite limitation, described at http://www.sqlalchemy.org/docs/reference/dialects/sqlite.html?highlight=sqlite#auto-incrementing-beahvior spelling correction: http://www.sqlalchemy.org/docs/reference/dialects/sqlite.html?highlight=sqlite#auto-incrementing-behavior from sqlalchemy import create_engine, Column,Integer, String, ForeignKey from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker,relation, backref engine = create_engine(sqlite:///:memory:,echo=False) Base=declarative_base() class Child(Base): __tablename__=Child id=Column(Integer,primary_key=True) class Association(Base): __tablename__=Association id=Column(Integer,primary_key=True) parent_id=Column(Integer,ForeignKey(Parent.id),primary_key=True) child_id=Column(Integer,ForeignKey(Child.id),primary_key=True) child=relation(Child,backref=parents) data=Column(String(32)) def __init__(self): self.data=some text class Parent(Base): __tablename__=Parent id=Column(Integer, primary_key=True) children=relation(Association,backref=backref(parent)) Base.metadata.create_all(engine) Session=sessionmaker(bind=engine) session = Session() p=Parent() a=Association() a.child=Child() p.children.append(a) session.add(p) session.query(Parent).all() I need the id for another 1:n realtion with the association object. What am I missing here? Thanks Sebastian -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] three primary keys on association object
Oh, thanks for the pointer. There's so much to read and learn being new to SQLAlchemy... Sorry for bugging. On Fri, 05 Mar 2010 15:49:03 +0100, Michael Bayer mike...@zzzcomputing.com wrote: Sebastian Elsner wrote: Hello, I have an association object declaratively with three primary keys, but on insert, the first (id) is not autoincremented. Please see test the code below known sqlite limitation, described at http://www.sqlalchemy.org/docs/reference/dialects/sqlite.html?highlight=sqlite#auto-incrementing-beahvior from sqlalchemy import create_engine, Column,Integer, String, ForeignKey from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker,relation, backref engine = create_engine(sqlite:///:memory:,echo=False) Base=declarative_base() class Child(Base): __tablename__=Child id=Column(Integer,primary_key=True) class Association(Base): __tablename__=Association id=Column(Integer,primary_key=True) parent_id=Column(Integer,ForeignKey(Parent.id),primary_key=True) child_id=Column(Integer,ForeignKey(Child.id),primary_key=True) child=relation(Child,backref=parents) data=Column(String(32)) def __init__(self): self.data=some text class Parent(Base): __tablename__=Parent id=Column(Integer, primary_key=True) children=relation(Association,backref=backref(parent)) Base.metadata.create_all(engine) Session=sessionmaker(bind=engine) session = Session() p=Parent() a=Association() a.child=Child() p.children.append(a) session.add(p) session.query(Parent).all() I need the id for another 1:n realtion with the association object. What am I missing here? Thanks Sebastian -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- Sebastian Elsner-pipeline td - r i s e | fx t: +49 30 20180300 sebast...@risefx.com c: +49 175 3365739 www.risefx.com r i s e | fx GmbH Schlesische Strasse 28 Aufgang B, 10997 Berlin Geschäftsführer: Sven Pannicke, Robert Pinnow Handelsregister Berlin HRB 106667 B -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] Re: Getting access to the object being updated inside a default callable?
Thanks for clarifying that. The MapperExtension is what I've been using so far for this, just wondered if there was a way to do this with column-level defaults. Now that I think about it though, the current way probably does make more sense, since if the values are dependent on outside influences, they cease to be column-level defaults. On Mar 5, 2:48 pm, Michael Bayer mike...@zzzcomputing.com wrote: Oliver Beattie wrote: Sorry to bug I imagine there is no way of doing this, but would be good to know for sure. If not, this would be really useful functionality. For instance, I might want to populate one column based on the contents of one of more other columns. On 12 Jan, 11:21, Oliver Beattie oli...@obeattie.com wrote: Hi there, I feel like I'm perhaps missing something, but I wonder if there's any way to access the object being updated inside a ColumnDefault? More specifically, if I have a let's call it DBObject (using declarative) which has a callable as its default, is there any way to access that DBObject instance inside the default function? I see it gets passed an ExecutionContext instance, but I don't see a way to get the object from there :\ If there's a way to do this, it would help me a lot :) The executioncontext has all the parameters for the whole statement, you can use those. But the ORM object is not available at that level. You might want to use MapperExtension.before_insert() if you need ORM-level awareness. Thanks, Oliver -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] graph data structure with many edge types
I am trying to model graph data structure where nodes can be connected by different types of edges. For example, we could have 2 nodes represnting persons: Alice and Bob and we could have 3 nodes representing projects: projectA, projectB, projectC. Alice is working on projectA and projectC. Bob is working on projectB and projectC. Alice is manager of projectA. Bob is manager of projectB. I would like to encode all this in 2 database tables: Node table: id name 1 Alice 2 Bob 3 projectA 4 projectB 5 projectC Edge table: n1_id n2_id edge_type 1 3 working_on 1 5 working_on 2 4 working_on 2 5 working_on 1 3 manager_of 2 4 manager_of (it would even by better to replace the edge_type by an edge_type_id and move them to a separate table, but I would already be very happy to get it to work like this) and I would like to be able to access all this as a dictionary of lists (or sets): alice = session.query(Node).filter_by(name=Alice).first() bob = session.query(Node).filter_by(name=Bob).first() alice.related['working_on'] [Node: 'projectA', Node: 'projectC', ] bob.related['working_on'] [Node: 'projectB', Node: 'projectC', ] alice.related['manager_of'] [Node: 'projectA', ] bob.related['manager_of'] [Node: 'projectB', ] and adding stuff: alice.related['working_on'].append(Node(projectD)) alice.related['working_on'] [Node: 'projectA', Node: 'projectC', Node: 'projectD', ] I think this must be doable using the association_proxy in some way (it's vaguely familiar to the Broker/Stock/Holding example in the documentation, but now the extra value in the linking table (shares) should be used as key in the dictionary) but I can't get it to work. Could somebody give me an idea if this is at all possible and maybe a push in the right direction? Many thanks, Jan. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] graph data structure with many edge types
JanW wrote:
I am trying to model graph data structure where nodes can be connected
by different types of edges.
I would like to encode all this in 2 database tables:
Node table:
Edge table:
I think this must be doable using the association_proxy in some way
(it's vaguely familiar to the Broker/Stock/Holding example in the
documentation, but now the extra value in the linking table (shares)
should be used as key in the dictionary) but I can't get it to work.
Could somebody give me an idea if this is at all possible and maybe a
push in the right direction?
We have a similar example, minus the type part, at
http://www.sqlalchemy.org/trac/browser/sqlalchemy/trunk/examples/graphs/directed_graph.py
.
So here you'd additionally use
collection_class=sqlalchemy.orm.collections.attribute_mapped_collection('edge_type')
for the node-edge collections. The association proxy can then eliminate
the edge traversal between node-node.
Many thanks,
Jan.
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[sqlalchemy] Re: insert defaults
Well it's something between the two. The instance variable
compressed will always be NULL when adding or updating an instance,
but I want it to infer a value from another instance variable. When
inserting... the value of 'compressed' in the sql statement needs to
be the raw SQL string COMPRESS('%s') % instance.text. It isn't
simply running it through a function... it's dynamically creating the
column value from the object's instance variables upon insert or
update. MySQL has some funky compression function so the insert value
for the column has to be raw sql.
On Mar 4, 3:30 pm, Michael Bayer mike...@zzzcomputing.com wrote:
patrick wrote:
Hey,
I'm trying to create dynamic defaults for columns ala http://
www.sqlalchemy.org/docs/metadata.html#context-sensitive-default-funct
MySQL has COMPRESS and UNCOMPRESS functions that I'm trying to
leverage. I don't want to compress with python's zlib because I have
legacy tables that were compressed using MySQL (which has a weird non-
standard zip header and body), and I need to interface with them.
Anyway, during an insert or update, I want to grab the 'text' variable
from the instance object and insert it into the database like:
COMPRESS(the text value). Obviously context.current_parameters is
not the appropriate object, but I can't figure out if it's possible to
access the instance being inserted/updated.
are you trying to create a *default* value for an INSERT/UPDATE when NULL
would otherwise be passed, or are you trying to run all incoming/outgoing
data through a SQL function ? those are two completely separate topics.
def compress_text(context):
return COMPRESS('%s') % context.current_parameters['text']
class Tree(BaseStruct, Base):
__tablename__ = 'tree'
__table_args__ = (
{'autoload':True}
)
compressed =
deferred(Column(Binary(),default=compress_text,default=compress_text,onupdate=compress_text))
text =
column_property(select([UNCOMPRESS(compressed)]),deferred=True)
Is this possible with 0.5.7?
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Re: [sqlalchemy] Re: insert defaults
On Mar 5, 2010, at 6:44 PM, patrick wrote:
Well it's something between the two. The instance variable
compressed will always be NULL when adding or updating an instance,
but I want it to infer a value from another instance variable. When
inserting... the value of 'compressed' in the sql statement needs to
be the raw SQL string COMPRESS('%s') % instance.text. It isn't
simply running it through a function... it's dynamically creating the
column value from the object's instance variables upon insert or
update. MySQL has some funky compression function so the insert value
for the column has to be raw sql.
so do a before_insert() mapper extension and set the attribute as needed to
func.compressed(instance.text). Or do the same at the object level, i.e user
sets myobject.foo, foo is a descriptor-enabled method which then sets
myobject.bar = func.compressed(foo) or whatever.
the technique here is
http://www.sqlalchemy.org/docs/session.html#embedding-sql-insert-update-expressions-into-a-flush
.
On Mar 4, 3:30 pm, Michael Bayer mike...@zzzcomputing.com wrote:
patrick wrote:
Hey,
I'm trying to create dynamic defaults for columns ala http://
www.sqlalchemy.org/docs/metadata.html#context-sensitive-default-funct
MySQL has COMPRESS and UNCOMPRESS functions that I'm trying to
leverage. I don't want to compress with python's zlib because I have
legacy tables that were compressed using MySQL (which has a weird non-
standard zip header and body), and I need to interface with them.
Anyway, during an insert or update, I want to grab the 'text' variable
from the instance object and insert it into the database like:
COMPRESS(the text value). Obviously context.current_parameters is
not the appropriate object, but I can't figure out if it's possible to
access the instance being inserted/updated.
are you trying to create a *default* value for an INSERT/UPDATE when NULL
would otherwise be passed, or are you trying to run all incoming/outgoing
data through a SQL function ? those are two completely separate topics.
def compress_text(context):
return COMPRESS('%s') % context.current_parameters['text']
class Tree(BaseStruct, Base):
__tablename__ = 'tree'
__table_args__ = (
{'autoload':True}
)
compressed =
deferred(Column(Binary(),default=compress_text,default=compress_text,onupdate=compress_text))
text =
column_property(select([UNCOMPRESS(compressed)]),deferred=True)
Is this possible with 0.5.7?
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