Re: [sqlalchemy] Getting the entity name, ideally the ORM class in the shard selector?

2013-04-23 Thread Rob Fowler 
 

So anyone else who asks this knows, the following works:

A query with just a column:

qq = session.query(Configuration.name)

Normally I would loop, but in this case, taking just the first column:

yy = qq.column_descriptions[0]['expr']

yy.expression.table.name

gives: ''configurations”


 Configuration.__table__.name

gives: ''configurations”


 All good, so we can compare on the underlying table names.


 Sorry to keep asking questions. If we wanted to do this using the ORM 
objects, is there a way to get the 'Configuration' object to compare to and 
not compare the strings with the underlying tables?


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Re: [sqlalchemy] Getting the entity name, ideally the ORM class in the shard selector?

2013-04-22 Thread Michael Bayer 
from that expr, assuming it's a Column,  you should be able to say 
attribute.expression.table, where "attribute" is that InstrumentedAttribute 
object.  

If it can be any kind of expression, then you'd need to look into some of the 
SQL utilities to find tables within the expression.


On Apr 22, 2013, at 8:01 PM, Rob Fowler  wrote:

> If the query does not have a table in it we don't get the tables.
> For example, the following simple query gets a list of connection_strings 
> column from the Connection table:
> 
> aa = session.query(Connection.connection_string)
> aa.column_descriptions
> 
> [{'aliased': False,
>   'expr': ,
>   'name': 'connection_string',
>   'type': String(length=100)}]
> 
> Exploring into the expr I am not sure how to get the table from that.
> 
> On Tuesday, 23 April 2013 02:32:15 UTC+10, Michael Bayer wrote:
> 
> 
> use column_descriptions: 
> http://docs.sqlalchemy.org/en/rel_0_8/orm/query.html#sqlalchemy.orm.query.Query.column_descriptions
> 
> 
> 
> 
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Re: [sqlalchemy] Getting the entity name, ideally the ORM class in the shard selector?

2013-04-22 Thread Rob Fowler 
If the query does not have a table in it we don't get the tables.
For example, the following simple query gets a list of connection_strings 
column from the Connection table:

aa = session.query(Connection.connection_string)
aa.column_descriptions

[{'aliased': False,
  'expr': ,
  'name': 'connection_string',
  'type': String(length=100)}]

Exploring into the expr I am not sure how to get the table from that.

On Tuesday, 23 April 2013 02:32:15 UTC+10, Michael Bayer wrote:
>
>
>
> use column_descriptions: 
> http://docs.sqlalchemy.org/en/rel_0_8/orm/query.html#sqlalchemy.orm.query.Query.column_descriptions
>
>
>
>

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Re: [sqlalchemy] Getting the entity name, ideally the ORM class in the shard selector?

2013-04-22 Thread Michael Bayer 

On Apr 21, 2013, at 10:04 PM, Rob Fowler  wrote:

> We are using the sharding module included in our application.
> 
> Currently we are selecting shards based on field. This works really well, as 
> the field that gets hashed to select the shard needs to be migrated to the 
> other tables that exist only in that shard.
> 
> Now we would like to have some static entities in all databases we would like 
> to use the table name to indicated that the table is available in all shards. 
> Ideally we would define a parent class 'unsharded' and derive from that class 
> for all the unsharded entities.
> 
> I can see the current entities are in _entities, but as that begins with an 
> underscore I don't think I am meant to be using it.
> 
> What should I use to get the entities from the query?
> 


use column_descriptions: 
http://docs.sqlalchemy.org/en/rel_0_8/orm/query.html#sqlalchemy.orm.query.Query.column_descriptions


> 
> ps. Loving sqlalchemy and just started setting up Alembic for our project 
> (flask, sqlalchemy, postgres).
> 
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>  
>  

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[sqlalchemy] Getting the entity name, ideally the ORM class in the shard selector?

2013-04-21 Thread Rob Fowler 
 

We are using the sharding module included in our application. 


Currently we are selecting shards based on field. This works really well, 
as the field that gets hashed to select the shard needs to be migrated to 
the other tables that exist only in that shard.


 Now we would like to have some static entities in all databases we would 
like to use the table name to indicated that the table is available in all 
shards. Ideally we would define a parent class 'unsharded' and derive from 
that class for all the unsharded entities.


 I can see the current entities are in _entities, but as that begins with 
an underscore I don't think I am meant to be using it. 


 What should I use to get the entities from the query?


ps. Loving sqlalchemy and just started setting up Alembic for our project 
(flask, sqlalchemy, postgres).

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