Re: [sqlalchemy] Clarification about performance and relation()
Excuse me,
After your valuable advice, i've modified my code and i've removed the
manual setting of the foreign key (which was completely wrong). But now
i've another problem, maybe due to another misunderstanding.
(I've moved all my ORM classes within the same module now).
I am parsing an xml where i can found something like:
definition id=1
..
platform Windows XP/platform
..
/definition
definition id=2
..
platform Linux/platform
..
/definition
definition id=3
..
platform Windows 7/platform
platform Windows XP/platform
platform Windows Vista/platform
..
/definition
When a single platform is associated to a definition (1:1), i expect the
following table layout:
table_platform:
id | platform| definitionId_fk
1 Windows XP1
2 Linux 2
When N platforms are associated to the same definition (N:1), i expect the
following table layout:
id | platform| definitionId_fk
3 Windows 7 3
4 Windows XP 3
5 Windows Vista3
5 Solaris 4
For the first case, everything works fine and i got exactly what i am
expecting but, for the second case i got:
id | platform| definitionId_fk
3 Windows 7 None
4 Windows XP None
5 Windows Vista3
Maybe it's a stupid problem but i can't figure it out at the moment :/
Code:
...
for definitions in ovalXML._childrenMap['definitions']:
for definition in definitions.getchildren():
defInst = ORM_Classes.DefinitionClass(definition)
...
if subElem1.tag == mainNS + platform:
platf = ORM_Classes.PlatformClass()
platf.setPlatform(str(subElem1))
defInst.PlatformRel = [platf]
session.add(defInst)
session.add(platf)
#i perform a commit every 1000 definitions as you suggested :)
DefinitionClass:
class DefinitionClass(Base):
__tablename__ = 'definitions'
defId = Column(Integer, primary_key=True)
...
version = Column(String)
PlatformRel = relation(PlatformClass, backref=definitions)
def __init__(self, node):
self.version = node.get(version)
...
PlatformClass:
class PlatformClass(Base):
__tablename__ = 'platform'
platformId = Column(Integer, primary_key=True)
platform = Column(String)
platformId_fk = Column('definitionId_fk', Integer,
ForeignKey('definitions.defId'))
def setPlatform(self, node):
self.platform = node
What can i do || correct to get the expected result?
Thanks for your patience.
---
Masetto
On Thu, Mar 25, 2010 at 4:56 PM, Michael Bayer mike...@zzzcomputing.comwrote:
the relationship between two tables requires both the ForeignKey to be
present as well as the relationship() (relation() in 0.5) function to be
present in the mapping.
masetto wrote:
From 30 mins to 2mins... shame :P
Thanks Micheal !
Forgive me, what about the other question about foreign keys?
On Thu, Mar 25, 2010 at 3:43 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
masetto wrote:
Hi all,
i am writing a python script which parse an xml file (python lxml) and
import it into a sqlite db, and it works.
The xml file size is about 30Mb and the import operation takes about
15
minutes (do you think is too much? is there something i can do to
speed
up
the process?)
This is a piece of the import function:
...
for definition in definitions.getchildren(): #iterate for every xml
children
node
defInst = SQLTableBuilder_Definition.DefinitionClass(definition)
#read
and write on db some attribute of the node
...
if subbaElem1.tag == mainNS + platform: #another loop iterate
for
every sub-node of the definition node
platf = SQLTableBuilder_Platform.PlatformClass()
platf.setPlatform(str(subbaElem1))
platf.platformId_fk = defInst.defId
session.add(platf)
session.commit()
...
session.add(defInst)
session.commit()
don't commit on every node and on every sub-node. Just commit once
every
1000 new objects or so. will save a ton of processing.
where DefinitionClass contains the attributes declaration
(primary_key,
column(string), etc.) and a Foreign Key.
There is a relation between the definition table and the platform
table
(one
or more platforms - Operating System - can be associated to a single
definition) so,
in the platform table, i've added the following: platformId_fk =
Column('definitionId_fk', Integer, ForeignKey('definitions.defId'))
All my ORM-Classes are declared within n different classes within n
different
Re: [sqlalchemy] Clarification about performance and relation()
Hi Masetto, On 26/03/2010 16:01, masetto wrote: Maybe it's a stupid problem but i can't figure it out at the moment :/ Code: ... for definitions in ovalXML._childrenMap['definitions']: for definition in definitions.getchildren(): defInst = ORM_Classes.DefinitionClass(definition) session.add(defInst) # I think this line should be here, you have it further down ... if subElem1.tag == mainNS + platform: platf = ORM_Classes.PlatformClass() platf.setPlatform(str(subElem1)) #defInst.PlatformRel = [platf]# change this to platf.definitions = defInst Werner -- 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] Clarification about performance and relation()
First of all, thanks for your answer :)
# defInst.PlatformRel = [platf]# change this to
platf.definitions = defInst
I don't have any definitions attribute within the PlatformClass, i suppose
you mean the foreign key, isnt'it?
That is
platf.platformId_fk = defInst
However, this results in another error:
sqlalchemy.exc.InterfaceError: (InterfaceError) Error binding parameter 1 -
probably unsupported type. u'INSERT INTO platform (platform,
definitionId_fk) VALUES (?, ?)' ['Microsoft Windows 2000',
ORM_Classes.DefinitionClass object at 0x8f5278c]
I've played a little with it, then i've moved the relation() from
DefinitionClass to PlatformClass:
class PlatformClass(Base):
__tablename__ = 'platform'
platformId = Column(Integer, primary_key=True)
platform = Column(String)
platformId_fk = Column('definitionId_fk', Integer,
ForeignKey('definitions.defId'))
PlatformRel = relation(DefinitionClass, backref=platform)
and then:
platf.PlatformRel = defInst
Now i got the expected data! It WORKS :P Thanks Werner!
But, i need to understand.. why now it's working?
From the doc:
We are also free... to define the
relationship()http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.relationshiponly
on one class and not the other. It is also possible to define two
separate
relationship()http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.relationshipconstructs
for either direction, which is generally safe for many-to-one and
one-to-many relationships, but not for many-to-many relationships.
Maybe i don't have well understood the role of the relation()/relationship()
function but, shouldn't be the same thing to define the relation() within
the DefinitionClass? I've only changed the location of the relation() and
now it works.
Can you kindly better explain me the role of the relationship() function?
Mmm... please correct me if i'm wrong:
- The relationship between the User and Address classes is defined
separately using the
relationship()http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.relationshipfunction
OK, and is the only way to define a relation between two tables.
- If i put relationship() in both classes i got a *bidirectional*relationship
- Because of the *placement* of the foreign key, from Address to User it is
*many to one*... !!! Oh, is this the point, right? If, in the same class,
i define a foreign key AND a relationship() i create a many to one relation
with the linked table
- ..., and from User to Address it is *one to many* - This is valid only
in the bidirectional case or it's automatic when i declare somewhere
foreign key + relationship() ?
- Initially i've defined the foreign key in the PlatformClass and the
relation() in the DefinitionClass. Which type of relation i've created in
that way?
Thanks again!
On Fri, Mar 26, 2010 at 4:50 PM, werner wbru...@free.fr wrote:
Hi Masetto,
On 26/03/2010 16:01, masetto wrote:
Maybe it's a stupid problem but i can't figure it out at the moment :/
Code:
...
for definitions in ovalXML._childrenMap['definitions']:
for definition in definitions.getchildren():
defInst = ORM_Classes.DefinitionClass(definition)
session.add(defInst) # I think this line should be here,
you have it further down
...
if subElem1.tag == mainNS + platform:
platf = ORM_Classes.PlatformClass()
platf.setPlatform(str(subElem1))
#defInst.PlatformRel = [platf]# change this to
platf.definitions = defInst
Werner
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Re: [sqlalchemy] Clarification about performance and relation()
masetto wrote:
defInst.PlatformRel = [platf]
dont you mean to be appending here ? definst.platformrel.append(platf)
session.add(defInst)
session.add(platf)
#i perform a commit every 1000 definitions as you suggested :)
DefinitionClass:
class DefinitionClass(Base):
__tablename__ = 'definitions'
defId = Column(Integer, primary_key=True)
...
version = Column(String)
PlatformRel = relation(PlatformClass, backref=definitions)
def __init__(self, node):
self.version = node.get(version)
...
PlatformClass:
class PlatformClass(Base):
__tablename__ = 'platform'
platformId = Column(Integer, primary_key=True)
platform = Column(String)
platformId_fk = Column('definitionId_fk', Integer,
ForeignKey('definitions.defId'))
def setPlatform(self, node):
self.platform = node
What can i do || correct to get the expected result?
Thanks for your patience.
---
Masetto
On Thu, Mar 25, 2010 at 4:56 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
the relationship between two tables requires both the ForeignKey to be
present as well as the relationship() (relation() in 0.5) function to
be
present in the mapping.
masetto wrote:
From 30 mins to 2mins... shame :P
Thanks Micheal !
Forgive me, what about the other question about foreign keys?
On Thu, Mar 25, 2010 at 3:43 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
masetto wrote:
Hi all,
i am writing a python script which parse an xml file (python lxml)
and
import it into a sqlite db, and it works.
The xml file size is about 30Mb and the import operation takes
about
15
minutes (do you think is too much? is there something i can do to
speed
up
the process?)
This is a piece of the import function:
...
for definition in definitions.getchildren(): #iterate for every xml
children
node
defInst =
SQLTableBuilder_Definition.DefinitionClass(definition)
#read
and write on db some attribute of the node
...
if subbaElem1.tag == mainNS + platform: #another loop iterate
for
every sub-node of the definition node
platf =
SQLTableBuilder_Platform.PlatformClass()
platf.setPlatform(str(subbaElem1))
platf.platformId_fk = defInst.defId
session.add(platf)
session.commit()
...
session.add(defInst)
session.commit()
don't commit on every node and on every sub-node. Just commit once
every
1000 new objects or so. will save a ton of processing.
where DefinitionClass contains the attributes declaration
(primary_key,
column(string), etc.) and a Foreign Key.
There is a relation between the definition table and the platform
table
(one
or more platforms - Operating System - can be associated to a
single
definition) so,
in the platform table, i've added the following: platformId_fk =
Column('definitionId_fk', Integer, ForeignKey('definitions.defId'))
All my ORM-Classes are declared within n different classes within n
different python modules so, i've included the needed imports
everytime i
needed it.
And i suppose this is a problem, at least for me, sometime, because
when
i
try to add: PlatformRel =
relation(SQLTableBuilder_Definition.DefinitionClass,
backref=platform)
within my platformClass, i got: 'list' object has no attribute
'_sa_instance_state' :/
So, i've tried to manually set the foreign key, as you can see
above.
In
the documentation (http://www.sqlalchemy.org/docs/ormtutorial.html)
i
read:
SQLAlchemy is automatically aware of many-to-one/one-to-many
based
on
foreign keys. Does this mean that what i've done is correct or i'm
a
little
confused? If i manually set a foreign key value, does sqlalchemy
understand that a relation between two tables exists?
Thanks for your attention.
---
Masetto
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Re: [sqlalchemy] Clarification about performance and relation()
Hi Masetto,
On 26/03/2010 17:43, masetto wrote:
First of all, thanks for your answer :)
You are welcome.
# defInst.PlatformRel = [platf]# change this to
platf.definitions = defInst
I don't have any definitions attribute within the PlatformClass, i
suppose you mean the foreign key, isnt'it?
Yes you do:)
You have/had this in your model:
PlatformRel = relation(PlatformClass, backref=definitions)
backref creates a relation called definitions in the PlatformClass.
That is
platf.platformId_fk = defInst
However, this results in another error:
sqlalchemy.exc.InterfaceError: (InterfaceError) Error binding
parameter 1 - probably unsupported type. u'INSERT INTO platform
(platform, definitionId_fk) VALUES (?, ?)' ['Microsoft Windows
2000', ORM_Classes.DefinitionClass object at 0x8f5278c]
I've played a little with it, then i've moved the relation() from
DefinitionClass to PlatformClass:
class PlatformClass(Base):
__tablename__ = 'platform'
platformId = Column(Integer, primary_key=True)
platform = Column(String)
platformId_fk = Column('definitionId_fk', Integer,
ForeignKey('definitions.defId'))
PlatformRel = relation(DefinitionClass, backref=platform)
and then:
platf.PlatformRel = defInst
Now i got the expected data! It WORKS :P Thanks Werner!
I think it should have worked the other way round too. But frankly I am
not an expert on SA, nor am I too comfortable just looking at code
fragments in an email.
But, i need to understand.. why now it's working?
From the doc:
We are also free... to define the relationship()
http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.relationship
only on one class and not the other. It is also possible to define two
separate relationship()
http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.relationship
constructs for either direction, which is generally safe for
many-to-one and one-to-many relationships, but not for many-to-many
relationships.
Maybe i don't have well understood the role of the
relation()/relationship() function but, shouldn't be the same thing to
define the relation() within the DefinitionClass? I've only changed
the location of the relation() and now it works.
Can you kindly better explain me the role of the relationship() function?
Let me try and I hope that others will jump in if I say something
misleading.
relationship() (or its old but still valid equivalent relation()) or the
new name relationship() allow you to define relationships between two
tables.
You could do it in one of the two table like this (this is what I do
most of the time):
define it in PlatformClass:
PlatformRel = relation(DefinitionClass, backref=platform) - this sets
up both relationships from PlatformClass to DefinitionClass (a
one-to-many) and from DefinitionClass to PlatformClass (a many-to-one).
or you could turn it around and define it in DefinitionClass:
DefinitionRel = relation(PlatfromClass, backref=definitions)
or do it in both tables like this:
PlatformRel = relation(DefinitionClass) - sets up the one-to-many
DefinitionRel = relation(PlatformClass) - sets up the many-to-one
Mmm... please correct me if i'm wrong:
- The relationship between the User and Address classes is defined
separately using the relationship()
http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.relationship
function
OK, and is the only way to define a relation between two tables.
- If i put relationship() in both classes i got a *bidirectional*
relationship
Or use backref
- Because of the *placement* of the foreign key, from Address to User
it is *many to one*... !!! Oh, is this the point, right? If, in the
same class, i define a foreign key AND a relationship() i create a
many to one relation with the linked table
- ..., and from User to Address it is *one to many* - This is valid
only in the bidirectional case or it's automatic when i declare
somewhere foreign key + relationship() ?
Defining the foreign key does NOT setup/define a relation().
- Initially i've defined the foreign key in the PlatformClass and the
relation() in the DefinitionClass. Which type of relation i've created
in that way?
It does really not matter in which class you define the relation().
What type it will be I showed higher up, but you should also look at
uselist in relationship() doc.
You might also want to look at the doc of:
http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.relationship
http://www.sqlalchemy.org/docs/reference/orm/mapping.html#sqlalchemy.orm.backref
I hope it helps and didn't cause more confusion.
Werner
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Re: [sqlalchemy] Clarification about performance and relation()
masetto wrote:
Hi all,
i am writing a python script which parse an xml file (python lxml) and
import it into a sqlite db, and it works.
The xml file size is about 30Mb and the import operation takes about 15
minutes (do you think is too much? is there something i can do to speed up
the process?)
This is a piece of the import function:
...
for definition in definitions.getchildren(): #iterate for every xml
children
node
defInst = SQLTableBuilder_Definition.DefinitionClass(definition) #read
and write on db some attribute of the node
...
if subbaElem1.tag == mainNS + platform: #another loop iterate for
every sub-node of the definition node
platf = SQLTableBuilder_Platform.PlatformClass()
platf.setPlatform(str(subbaElem1))
platf.platformId_fk = defInst.defId
session.add(platf)
session.commit()
...
session.add(defInst)
session.commit()
don't commit on every node and on every sub-node. Just commit once every
1000 new objects or so. will save a ton of processing.
where DefinitionClass contains the attributes declaration (primary_key,
column(string), etc.) and a Foreign Key.
There is a relation between the definition table and the platform table
(one
or more platforms - Operating System - can be associated to a single
definition) so,
in the platform table, i've added the following: platformId_fk =
Column('definitionId_fk', Integer, ForeignKey('definitions.defId'))
All my ORM-Classes are declared within n different classes within n
different python modules so, i've included the needed imports everytime i
needed it.
And i suppose this is a problem, at least for me, sometime, because when i
try to add: PlatformRel =
relation(SQLTableBuilder_Definition.DefinitionClass, backref=platform)
within my platformClass, i got: 'list' object has no attribute
'_sa_instance_state' :/
So, i've tried to manually set the foreign key, as you can see above. In
the documentation (http://www.sqlalchemy.org/docs/ormtutorial.html) i
read:
SQLAlchemy is automatically aware of many-to-one/one-to-many based on
foreign keys. Does this mean that what i've done is correct or i'm a
little
confused? If i manually set a foreign key value, does sqlalchemy
understand that a relation between two tables exists?
Thanks for your attention.
---
Masetto
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Re: [sqlalchemy] Clarification about performance and relation()
From 30 mins to 2mins... shame :P
Thanks Micheal !
Forgive me, what about the other question about foreign keys?
On Thu, Mar 25, 2010 at 3:43 PM, Michael Bayer mike...@zzzcomputing.comwrote:
masetto wrote:
Hi all,
i am writing a python script which parse an xml file (python lxml) and
import it into a sqlite db, and it works.
The xml file size is about 30Mb and the import operation takes about 15
minutes (do you think is too much? is there something i can do to speed
up
the process?)
This is a piece of the import function:
...
for definition in definitions.getchildren(): #iterate for every xml
children
node
defInst = SQLTableBuilder_Definition.DefinitionClass(definition)
#read
and write on db some attribute of the node
...
if subbaElem1.tag == mainNS + platform: #another loop iterate for
every sub-node of the definition node
platf = SQLTableBuilder_Platform.PlatformClass()
platf.setPlatform(str(subbaElem1))
platf.platformId_fk = defInst.defId
session.add(platf)
session.commit()
...
session.add(defInst)
session.commit()
don't commit on every node and on every sub-node. Just commit once every
1000 new objects or so. will save a ton of processing.
where DefinitionClass contains the attributes declaration (primary_key,
column(string), etc.) and a Foreign Key.
There is a relation between the definition table and the platform table
(one
or more platforms - Operating System - can be associated to a single
definition) so,
in the platform table, i've added the following: platformId_fk =
Column('definitionId_fk', Integer, ForeignKey('definitions.defId'))
All my ORM-Classes are declared within n different classes within n
different python modules so, i've included the needed imports everytime i
needed it.
And i suppose this is a problem, at least for me, sometime, because when
i
try to add: PlatformRel =
relation(SQLTableBuilder_Definition.DefinitionClass, backref=platform)
within my platformClass, i got: 'list' object has no attribute
'_sa_instance_state' :/
So, i've tried to manually set the foreign key, as you can see above.
In
the documentation (http://www.sqlalchemy.org/docs/ormtutorial.html) i
read:
SQLAlchemy is automatically aware of many-to-one/one-to-many based on
foreign keys. Does this mean that what i've done is correct or i'm a
little
confused? If i manually set a foreign key value, does sqlalchemy
understand that a relation between two tables exists?
Thanks for your attention.
---
Masetto
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Re: [sqlalchemy] Clarification about performance and relation()
the relationship between two tables requires both the ForeignKey to be
present as well as the relationship() (relation() in 0.5) function to be
present in the mapping.
masetto wrote:
From 30 mins to 2mins... shame :P
Thanks Micheal !
Forgive me, what about the other question about foreign keys?
On Thu, Mar 25, 2010 at 3:43 PM, Michael Bayer
mike...@zzzcomputing.comwrote:
masetto wrote:
Hi all,
i am writing a python script which parse an xml file (python lxml) and
import it into a sqlite db, and it works.
The xml file size is about 30Mb and the import operation takes about
15
minutes (do you think is too much? is there something i can do to
speed
up
the process?)
This is a piece of the import function:
...
for definition in definitions.getchildren(): #iterate for every xml
children
node
defInst = SQLTableBuilder_Definition.DefinitionClass(definition)
#read
and write on db some attribute of the node
...
if subbaElem1.tag == mainNS + platform: #another loop iterate
for
every sub-node of the definition node
platf = SQLTableBuilder_Platform.PlatformClass()
platf.setPlatform(str(subbaElem1))
platf.platformId_fk = defInst.defId
session.add(platf)
session.commit()
...
session.add(defInst)
session.commit()
don't commit on every node and on every sub-node. Just commit once
every
1000 new objects or so. will save a ton of processing.
where DefinitionClass contains the attributes declaration
(primary_key,
column(string), etc.) and a Foreign Key.
There is a relation between the definition table and the platform
table
(one
or more platforms - Operating System - can be associated to a single
definition) so,
in the platform table, i've added the following: platformId_fk =
Column('definitionId_fk', Integer, ForeignKey('definitions.defId'))
All my ORM-Classes are declared within n different classes within n
different python modules so, i've included the needed imports
everytime i
needed it.
And i suppose this is a problem, at least for me, sometime, because
when
i
try to add: PlatformRel =
relation(SQLTableBuilder_Definition.DefinitionClass,
backref=platform)
within my platformClass, i got: 'list' object has no attribute
'_sa_instance_state' :/
So, i've tried to manually set the foreign key, as you can see
above.
In
the documentation (http://www.sqlalchemy.org/docs/ormtutorial.html) i
read:
SQLAlchemy is automatically aware of many-to-one/one-to-many based
on
foreign keys. Does this mean that what i've done is correct or i'm a
little
confused? If i manually set a foreign key value, does sqlalchemy
understand that a relation between two tables exists?
Thanks for your attention.
---
Masetto
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