Changing adapters in ActiveRecord does not change the generated sql

Rails
1

If I establish a new connection with a new adapter (ie. switch from
mysql to
postgresl) the generated sql is still mysql specific. I tried all sorts
of
reset methods on AR::Base but to no avail. There must be something
being
memoized on ActiveRecord base that has to do with the adapter and it
doesn’t
get cleared when you establish a connection with a new adapter.

I know this isn’t standard behaviour, in fact the only reason I need
this is
because I’m writing a multi-tenancy
gemhttps://github.com/bradrobertson/apartmentfor rails that supports
many different database adapters. My tests run
through these adapters, but the 2nd adapter to be tested always fails
with
invalid sql.

Here’s an example:

ActiveRecord::Base.establish_connection :adapter => ‘mysql2’, :database
=>
‘my_test_db’, :username => ‘root’, :password => ‘’
User.scoped.to_sql #=> “SELECT users.* FROM users”
ActiveRecord::Base.establish_connection :adapter => ‘postgresql’,
:database
=> ‘my_test_db’, :username => ‘root’, :password => ‘’
User.scoped.to_sql #=> “SELECT users.* FROM users”

These back ticks on column names are mysql specific and are invalid for
postgresql, so it throws an error.

Does anyone know how to fully clear out whatever it is that is caching
this
sql being generated??

I searched through the source and was able to unset @quoted_table_name
on
the user model, this regenerated the table name properly, however the
query
now looks like:

User.scoped.to_sql #=> “SELECT "users".* FROM users”

Still not perfect. And I also don’t want to have to go through each
model
and unset a bunch of vars. Any simpler way to reload these?

2

On Sep 13, 4:29pm, Bradley [email protected] wrote:

Still not perfect. And I also don’t want to have to go through each model
and unset a bunch of vars. Any simpler way to reload these?

You could try calling reset_column_information (although it looks like
this doesn’t clear out quoted table name)

Fred

3

ya that doesn’t appear to help. especially if I’m just selecting *

4

I started looking into the
reload!http://api.rubyonrails.org/classes/Object.html#method-i-reload-21method
as I figured maybe manually reloading the classes in between testing
adapters would help.

In the dev console doing a reload appears to be similar to resetting the
quoted_table_name, I get the same:

User.scoped.to_sql #=> “SELECT "users".* FROM users”

So it’s caching that table_name (in the FROM clause) somewhere else
(that
isn’t reloaded)

Does anyone have any insight into this? I’m digging into the source but
I’m
not having a ton of luck.

5

I’ve found out something very interesting. If I’m first connected to
Postgresql, then switch to Mysql, I can reset both table and column
names
properly using

Model.reset_column_information

and

Model.reset_table_name

This gives me the proper backquoted columns/table names for Mysql.

User.scoped.to_sql #=> "SELECT users.* FROM users"

If however, I switch back to Postgresql, and run the same commands, it
doesn’t actually reset the column information properly, only the
table_name.

User.scoped.to_sql #=> "SELECT “users”.* FROM users"

I’ve found that it actually doesn’t matter in which order this happens.
The
first switch to one adapter allows me to reset properly. The second
switch
however does NOT.