[sqlalchemy] Load parent on child deletion
Hi! I have a model with a parent-child relationship on the same entity. The children collection on a parent instance has events set to intercept adding and removing instances to/from it. This is needed to update an attribute from the parent instance. But when I delete an instance which is the child of another one, that parent instance is not notified of its child removal and so the event is not fired. I tried working with the cascade rules but I have not been successful. Is this behaviour supported? Thanks! Pau. -- -- Pau Tallada Crespí Dep. d'Astrofísica i Cosmologia Port d'Informació Científica (PIC) Tel: +34 93 586 8233 -- -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@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] with_lockmode('share') ?
Hello,
I'm using SQLAlchemy 0.7.6 and PostgreSQL 9.0.7 which support a FOR
UPDATE and a FOR SHARE clause to lock selected rows.
I noticed that the .with_lockmode() method of the Query object
(http://docs.sqlalchemy.org/en/latest/orm/query.html?highlight=with_lock#sqlalchemy.orm.query.Query.with_lockmode)
only accepts 'update' for PostgreSQL. Could it be an oblivion .. ?
(I tried with the .with_lockmode('read'), but it also generates a FOR
UPDATE on PostgreSQL)
Thank you,
Julien
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[sqlalchemy] Single table inheritance
Hoping for advice: I'm using sqlalchemy against a legacy application's database design, most of which isn't in my control. I have a situation where single table inheritance should work beautifully but there is one catch: of the 7 polymorphic sub classes, there is one which is allowed to change into another. The rest are immutable. As an example, suppose a Employee were allowed to be promoted to Manager. The docs state that the polymorphic_identity is a read only attribute and that Behavior is undefined if directly modified. I could work around this by mapping 2 polymorphic_identities to one class, but as far a I can see, this can only be a single scalar value. The docs say that polymorphic_on may also be of other types besides Column in a future SQLAlchemy release... I wonder if I can help sqla map either of 2 values to a class in this way? Any advice? -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To view this discussion on the web visit https://groups.google.com/d/msg/sqlalchemy/-/vU1nLi3v8sEJ. To post to this group, send email to sqlalchemy@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] Single table inheritance
On Mar 21, 2012, at 9:49 AM, Kent wrote: Hoping for advice: I'm using sqlalchemy against a legacy application's database design, most of which isn't in my control. I have a situation where single table inheritance should work beautifully but there is one catch: of the 7 polymorphic sub classes, there is one which is allowed to change into another. The rest are immutable. As an example, suppose a Employee were allowed to be promoted to Manager. The docs state that the polymorphic_identity is a read only attribute and that Behavior is undefined if directly modified. I could work around this by mapping 2 polymorphic_identities to one class, but as far a I can see, this can only be a single scalar value. The docs say that polymorphic_on may also be of other types besides Column in a future SQLAlchemy release... I wonder if I can help sqla map either of 2 values to a class in this way? Any advice? did you try just saying employee.type = 'manager', flushing, then loading a new copy of it ? also polymorphic_on can be any SQL expression in 0.7, like a CASE statement if you wanted. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@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] with_lockmode('share') ?
the PG dialect has only FOR UPDATE and FOR UPDATE NOWAIT at the moment,
easy enough to add more options though it would be helpful if someone could
volunteer a patch on it (with tests as always!):
http://www.sqlalchemy.org/trac/ticket/2445
On Mar 21, 2012, at 6:00 AM, Julien Cigar wrote:
Hello,
I'm using SQLAlchemy 0.7.6 and PostgreSQL 9.0.7 which support a FOR UPDATE
and a FOR SHARE clause to lock selected rows.
I noticed that the .with_lockmode() method of the Query object
(http://docs.sqlalchemy.org/en/latest/orm/query.html?highlight=with_lock#sqlalchemy.orm.query.Query.with_lockmode)
only accepts 'update' for PostgreSQL. Could it be an oblivion .. ?
(I tried with the .with_lockmode('read'), but it also generates a FOR UPDATE
on PostgreSQL)
Thank you,
Julien
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Re: [sqlalchemy] Load parent on child deletion
On Mar 21, 2012, at 5:18 AM, Pau Tallada wrote: Hi! I have a model with a parent-child relationship on the same entity. The children collection on a parent instance has events set to intercept adding and removing instances to/from it. This is needed to update an attribute from the parent instance. But when I delete an instance which is the child of another one, that parent instance is not notified of its child removal and so the event is not fired. I tried working with the cascade rules but I have not been successful. Is this behaviour supported? delete an instance, meaning, parent.children.append(child) session.delete(child) session.commit() ? in that case no, parent.children is not notified of a collection removal, since no collection alteration actually takes place. The child is still there in parent.collection until the whole of parent is expired, which occurs after the commit(). See http://docs.sqlalchemy.org/en/latest/orm/session.html#deleting-from-collections for detailed discussion on this. Your two options here are to stick to collection mutations, or do an additional before_flush() or after_flush() event that goes through child objects marked deleted, finds their parents, and does what is needed. Thanks! Pau. -- -- Pau Tallada Crespí Dep. d'Astrofísica i Cosmologia Port d'Informació Científica (PIC) Tel: +34 93 586 8233 -- -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@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 sqlalchemy@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] with_lockmode('share') ?
Hi Mike,
I would be happy to provide a patch (when I find some time).
I never made any patch for SQLAlchemy, what's the preferred method to do
it? Attach an `hg diff` to the ticket or a pull request on Bitbucket .. ?
Thanks,
Julien
On 03/21/2012 15:08, Michael Bayer wrote:
the PG dialect has only FOR UPDATE and FOR UPDATE NOWAIT at the moment,
easy enough to add more options though it would be helpful if someone could volunteer a patch on it
(with tests as always!):
http://www.sqlalchemy.org/trac/ticket/2445
On Mar 21, 2012, at 6:00 AM, Julien Cigar wrote:
Hello,
I'm using SQLAlchemy 0.7.6 and PostgreSQL 9.0.7 which support a FOR UPDATE and
a FOR SHARE clause to lock selected rows.
I noticed that the .with_lockmode() method of the Query object
(http://docs.sqlalchemy.org/en/latest/orm/query.html?highlight=with_lock#sqlalchemy.orm.query.Query.with_lockmode)
only accepts 'update' for PostgreSQL. Could it be an oblivion .. ?
(I tried with the .with_lockmode('read'), but it also generates a FOR UPDATE on
PostgreSQL)
Thank you,
Julien
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Re: [sqlalchemy] Single table inheritance
That will work for me, thanks! P.S. make a note that the doc statement that it will be a future release should be updated. On 3/21/2012 10:04 AM, Michael Bayer wrote: also polymorphic_on can be any SQL expression in 0.7, like a CASE statement if you wanted. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@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] Single table inheritance
On Mar 21, 2012, at 10:29 AM, Kent Bower wrote: That will work for me, thanks! P.S. make a note that the doc statement that it will be a future release should be updated. can you point me right to where it says that On 3/21/2012 10:04 AM, Michael Bayer wrote: also polymorphic_on can be any SQL expression in 0.7, like a CASE statement if you wanted. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@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 sqlalchemy@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] Load parent on child deletion
Yes, I meant that :P I'll try with the before_flush_event. Thanks!! 2012/3/21 Michael Bayer mike...@zzzcomputing.com On Mar 21, 2012, at 5:18 AM, Pau Tallada wrote: Hi! I have a model with a parent-child relationship on the same entity. The children collection on a parent instance has events set to intercept adding and removing instances to/from it. This is needed to update an attribute from the parent instance. But when I delete an instance which is the child of another one, that parent instance is not notified of its child removal and so the event is not fired. I tried working with the cascade rules but I have not been successful. Is this behaviour supported? delete an instance, meaning, parent.children.append(child) session.delete(child) session.commit() ? in that case no, parent.children is not notified of a collection removal, since no collection alteration actually takes place. The child is still there in parent.collection until the whole of parent is expired, which occurs after the commit(). See http://docs.sqlalchemy.org/en/latest/orm/session.html#deleting-from-collectionsfor detailed discussion on this. Your two options here are to stick to collection mutations, or do an additional before_flush() or after_flush() event that goes through child objects marked deleted, finds their parents, and does what is needed. Thanks! Pau. -- -- Pau Tallada Crespí Dep. d'Astrofísica i Cosmologia Port d'Informació Científica (PIC) Tel: +34 93 586 8233 -- -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@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 sqlalchemy@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. -- -- Pau Tallada Crespí Dep. d'Astrofísica i Cosmologia Port d'Informació Científica (PIC) Tel: +34 93 586 8233 -- -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@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: Access denied for user error
I tried sqlit. it is fine.
engine = create_engine('sqlite+pysqlite:///file.db')
but, MySQL can't connect.
2012年3月21日水曜日12時46分23秒 UTC+9 shinriyo:
Hi there
I use sqlalchemy and Python3.2 and pymysql on Windows7.
I tried below
from sqlalchemy import *
engine = create_engine('mysql+pymysql://teaspoon:teaspoon@localhost/teaspoon')
metadata = MetaData()
t = Table('mytable', metadata,
Column('mytable_id', Integer, primary_key=True)
)
metadata.create_all(engine)
But, error occurd
sqlalchemy.exc.InternalError: (InternalError) (1045, #28000Access denied for
user 'teaspoon'@'localhost' (using password: YES)) None None
So, I tried via console. (DOSprompt)
*It it connect? = It is OK!*
c:\xampp\mysql\bin\mysql.exe -u teaspoon -p
*Can user use database? = It is OK!*
mysql use teaspoon
Database changed
*Can user create? = It is OK!*
mysql CREATE TABLE teaspoon(id INT(11)
Query OK, 0 rows affected (0.07 sec)
I have no idea.
*Would you tell me why mysql deny?*
2012年3月21日水曜日12時46分23秒 UTC+9 shinriyo:
Hi there
I use sqlalchemy and Python3.2 and pymysql on Windows7.
I tried below
from sqlalchemy import *
engine = create_engine('mysql+pymysql://teaspoon:teaspoon@localhost/teaspoon')
metadata = MetaData()
t = Table('mytable', metadata,
Column('mytable_id', Integer, primary_key=True)
)
metadata.create_all(engine)
But, error occurd
sqlalchemy.exc.InternalError: (InternalError) (1045, #28000Access denied for
user 'teaspoon'@'localhost' (using password: YES)) None None
So, I tried via console. (DOSprompt)
*It it connect? = It is OK!*
c:\xampp\mysql\bin\mysql.exe -u teaspoon -p
*Can user use database? = It is OK!*
mysql use teaspoon
Database changed
*Can user create? = It is OK!*
mysql CREATE TABLE teaspoon(id INT(11)
Query OK, 0 rows affected (0.07 sec)
I have no idea.
*Would you tell me why mysql deny?*
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Re: [sqlalchemy] Re: Access denied for user error
it seems like you connect without a host using mysql.exe, so try:
create_engine('mysql+pymysql://teaspoon:teaspoon@/teaspoon')
otherwise you need to add an entry for 'teaspoon'@'localhost' to your user
table:
http://dev.mysql.com/doc/refman/5.0/en/connection-access.html
On Mar 21, 2012, at 10:48 PM, shinriyo wrote:
I tried sqlit. it is fine.
engine = create_engine('sqlite+pysqlite:///file.db')
but, MySQL can't connect.
2012年3月21日水曜日12時46分23秒 UTC+9 shinriyo:
Hi there
I use sqlalchemy and Python3.2 and pymysql on Windows7.
I tried below
from sqlalchemy import *
engine = create_engine('mysql+pymysql://teaspoon:teaspoon@localhost/teaspoon')
metadata = MetaData()
t = Table('mytable', metadata,
Column('mytable_id', Integer, primary_key=True)
)
metadata.create_all(engine)
But, error occurd
sqlalchemy.exc.InternalError: (InternalError) (1045, #28000Access denied for
user 'teaspoon'@'localhost' (using password: YES)) None None
So, I tried via console. (DOSprompt)
It it connect? = It is OK!
c:\xampp\mysql\bin\mysql.exe -u teaspoon -p
Can user use database? = It is OK!
mysql use teaspoon
Database changed
Can user create? = It is OK!
mysql CREATE TABLE teaspoon(id INT(11)
Query OK, 0 rows affected (0.07 sec)
I have no idea.
Would you tell me why mysql deny?
2012年3月21日水曜日12時46分23秒 UTC+9 shinriyo:
Hi there
I use sqlalchemy and Python3.2 and pymysql on Windows7.
I tried below
from sqlalchemy import *
engine = create_engine('mysql+pymysql://teaspoon:teaspoon@localhost/teaspoon')
metadata = MetaData()
t = Table('mytable', metadata,
Column('mytable_id', Integer, primary_key=True)
)
metadata.create_all(engine)
But, error occurd
sqlalchemy.exc.InternalError: (InternalError) (1045, #28000Access denied for
user 'teaspoon'@'localhost' (using password: YES)) None None
So, I tried via console. (DOSprompt)
It it connect? = It is OK!
c:\xampp\mysql\bin\mysql.exe -u teaspoon -p
Can user use database? = It is OK!
mysql use teaspoon
Database changed
Can user create? = It is OK!
mysql CREATE TABLE teaspoon(id INT(11)
Query OK, 0 rows affected (0.07 sec)
I have no idea.
Would you tell me why mysql deny?
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Re: [sqlalchemy] Re: Access denied for user error
*
Hi Michael Bayer
Thank you for your help.
I tried to change create_engine args you suggested below.
create_engine('mysql+pymysql://teaspoon:teaspoon@/teaspoon')
But, same problem was happened.
So, I create user table like the URL you tought me.
---
CREATE TABLE user
(
user VARCHAR(64),
host VARCHAR(64)
);
INSERT INTO user VALUE ('teaspoon', 'localhost');
---
But, I couldn't resolve.
*
it seems like you connect without a host using mysql.exe, so try:
create_engine('mysql+pymysql://teaspoon:teaspoon@/teaspoon')
otherwise you need to add an entry for 'teaspoon'@'localhost' to your user
table:
http://dev.mysql.com/doc/refman/5.0/en/connection-access.html
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