On Jan 5, 2013, at 1:53 PM, Alexander Jacob wrote:
>
> I preferred the event solution but
>
> class Country(Base):
> __tablename__ = 'country'
> name = Column('name_<I18N>', String(64))
>
> 'SELECT country.`name_<I18N>` AS `country_name_<I18N>`, country.id AS
> country_id, country.iso2 AS country_iso2
> FROM country
> WHERE country.id = %s'
>
> gets properly replace in before_cursor_execute to
>
> 'SELECT country.`name_en` AS `country_name_en`, country.id AS country_id,
> country.iso2 AS country_iso2
> FROM country
> WHERE country.id = %s'
ah yeah. there's a way to manipulate the column lookup as well here which is
inside of the "context" passed to the event, I seem to recall working this out
for someone but I'd have to re-think into a recipe here. It starts using
things that aren't 100% public, though. or you could try a more elaborate
regexp that skips the label names, or one that does a second replace for
"tablename_colname_en" back to the original symbol since that's the labeling
scheme.
but before I get into that....
>
> This will work but this will load all columns from the db...
because your country is a fixed global, you can actually just map the column
here as needed:
class Country(Base):
# ...
name = Column('name_%s' % GLOBAL_COUNTRY, String)
then you don't even declare the other columns on this Table, how about that ?
there's also ways to have the columns on the Table, but not mapped, using
exclude_columns.
otherwise, if GLOBAL_COUNTRY changes at runtime, deferred() might be an
approach:
class Country(Base):
# ...
name_de = deferred(Column(String))
name_en = deferred(Column(String))
name_de and name_en won't be part of queries, and only load when they are
accessed. but this emits a second SELECT. You'd probably want some way to
undefer the one you need at Query time, that looks like this:
query(Country).options(undefer(Country.name_en))
but you'd probably want to automate that somehow.
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