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problems with aliased joins
Named scopes are designed to be chained together in any order/combination. If you join a table in one scope, and join the same table in another scope, it selects the same table twice and fails.
You can alias each join to a different name, but this leads to large number of more-or-less identical joins.
Solution: allow joins to be passed in string-array form:
named_scope :something {:join => ["INNER JOIN x", "INNER JOIN y", ...]}
named_scope :something_else {:join => "INNER JOIN x"}
# calling Model.something.something_else should only join in x once
Build a complete list of joins as an array from the beginning of the scoping process. Carry the array all the way to add_joins! where the list of string-joins is uniqued and finally converted into a single string.
This doesn't solve the aliasing issues with using :join => :assoc AND :join => "INNER JOIN assoc_table...".
-David Stevenson & Joseph Palermo from PivotalLabs
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Michael Koziarski- Assigned user set to Michael Koziarski
So silently removing the duplicates is always safe? There aren't any situations where we should be raising or warning the developer?
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Joseph PalermoSince the merged includes have to be string identical, it's just as safe or safer to always merge when possible.
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David Stevenson
Here you go. Thanks!
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Repository
- State changed from new to committed
(from [487758b3b88a38da3a75900839aea03774904fe1]) Allowed passing arrays-of-strings to :join everywhere. Merge duplicate join strings to avoid table aliasing problems.
Signed-off-by: Michael Koziarski michael@koziarski.com [#1077 problems with aliased joins state:committed] http://github.com/rails/rails/co...
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JensC
- Title changed from Chaining scopes with duplicate joins causes alias problem to problems with aliased joins
Hi,
I have two associations between two tables. One is a one to many and the other is many to may through. To be able to use named_scopes I must have aliased joins to address the right attribute. However if I do, rails avoids to have the two different joins because it thinks its a duplication of the joins.
Here is an example:
search members in one or many country
scope = scope.scoped( :conditions => ["property_country.short IN (?)", country_keys], :joins => 'INNER JOIN countries AS property_country ON property_country.id = memberships.property_country_id' ) if country_keys.size > 0
my_country
scope = scope.scoped( :conditions => ["vacation_countries.short = ?", my_country], :joins => "INNER JOIN join_vacation_countries ON (memberships.id = join_vacation_countries.membership_id) INNER JOIN countries AS vacation_countries ON (vacation_countries.id = join_vacation_countries.country_id)" ) unless my_country.blank?
I guess that is a limitation of the patch above and needs further refinement.
Thanks Jens
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Michael Koziarski
- State changed from committed to open
JensC: Can you provide us with a test case for active record which demonstrates this bug.
David & Joseph: Any thoughts?
Moving to block 2.2 final
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David Stevenson
Koz & Jens,
I'm afraid I don't see the issue that Jens is trying to show us. The patch that we submitted simply removes two completely-string-identical joins. These two would be removed:
scope = scope.scoped(:joins => "INNER JOIN countries AS country1 ON something") scope = scope.scoped(:joins => "INNER JOIN countries AS country1 ON something")These two would not be removed, as they are not string identical:
scope = scope.scoped(:joins => "INNER JOIN countries AS country1 ON something") scope = scope.scoped(:joins => "INNER JOIN countries AS country2 ON something")It's a very conservative removal. If an association generates a join, and a named scope also includes a string identical join, they will of course be "uniq"d into a single join (which should not have any negative consequences, since one copy is still included). It even does not remove them in this case, when they should be obviously removed:
scope = scope.scoped(:joins => "INNER JOIN countries AS country1 ON something") scope = scope.scoped(:joins => "INNER JOIN countries AS country1 ON something INNER JOIN something_else ON whatever")The "right" way to write the above so that they are uniq'd would be this:
scope = scope.scoped(:joins => "INNER JOIN countries AS country1 ON something") scope = scope.scoped(:joins => ["INNER JOIN countries AS country1 ON something", "INNER JOIN something_else ON whatever"])Can I get some clarification, perhaps a failing test on what the issue is from Jens?
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Michael Koziarski
Neither, it seems it should work to me...
Jens, can you please give us an example either in the rails tests or a simple stand-alone application?
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JensC
Oh hell! After creating an example that should show exactly what doesn't work ... it worked! After some more digging I noticed in my environment.rb that I still had
RAILS_GEM_VERSION = '2.1.2' unless defined? RAILS_GEM_VERSION
defined. It works in 2.2.0 RC 1. I am soooo sorry for that :-/. Next time I promise to provide an example before starting a bug report.
Once again sorry guys anf Thnx a lot. Jens
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DHH- State changed from open to invalid
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David Stevenson
DHH - Why did you just mark this invalid? Jens said there was no actual bug, and he made a mistake in commenting on this at all?
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Michael Koziarski
- State changed from open to committed