I'm working with a database I have no control over, and cannot make alterations to. This database has a table called warehouse_items. Each warehouse item is uniquely identified by a primary key indicating the item id.
Unfortunately, that primary key attribute is named WAREHOUSE_ITEM.ID
(Note the obnoxious period between "item" and "id")
When I try to run a basic query, such as:
WarehouseItem.find('wh3453')
I get an Undefined Table error.
Fortunately, when looking at what Rails is attempting to do, the problem becomes obvious:
: SELECT "warehouse_items".* FROM "warehouse_items" WHERE "WAREHOUSE_ITEM"."ID" = $1 LIMIT $2
Because of the period in the attribute name, Rails is treating "WAREHOUSE_ITEM.ID" as a table/attribute combination, rather than an attribute name with a period in it.
When I run the following PSQL query by hand, I get exactly what I need:
SELECT "warehouse_items".* FROM "warehouse_items" WHERE "warehouse_items"."WAREHOUSE_ITEM.ID" = 'wh3453'
Why is Rails screwing this up, and how can I fix it?
EDIT:
Also worth noting: I've tried using self.primary_key to override the primary key to no avail.
I've tried both a string and a symbol, as in:
self.primary_key="WAREHOUSE_ITEM.ID"
and
self.primary_key=:"WAREHOUSE_ITEM.ID"
Neither one has worked...
Thanks for all the help, everyone!
A suggestion in the comments to use find_by_sql does work! However, I stumbled onto a different solution that works even better.
First, I aliased the annoying attribute name to something simple: id
alias_attribute :id, :"WAREHOUSE_ITEM.ID"
Notice that it's still a symbol, which is important for the next step.
I then overwrite the primary_key method with a custom function:
def self.primary_key
return "id"
end
Now, when I do WarehouseItem.find('wh3453'), Rails defaults to checking id, which is aliased to the correct symbol and it works as intended!!!
Related
I am building a Rails app with the following models:
# vote.rb
class Vote < ApplicationRecord
belongs_to :person
belongs_to :show
scope :fulfilled, -> { where(fulfilled: true) }
scope :unfulfilled, -> { where(fulfilled: false) }
end
# person.rb
class Person < ApplicationRecord
has_many :votes, dependent: :destroy
def self.order_by_votes(show = nil)
count = 'nullif(votes.fulfilled, true)'
count = "case when votes.show_id = #{show.id} AND NOT votes.fulfilled then 1 else null end" if show
people = left_joins(:votes).group(:id).uniq!(:group)
people = people.select("people.*, COUNT(#{count}) AS people.vote_count")
people.order('people.vote_count DESC')
end
end
The idea behind order_by_votes is to sort People by the number of unfulfilled votes, either counting all votes, or counting only votes associated with a given Show.
This seem to work fine when I test against SQLite. But when I switch to Postgres I get this error:
Error:
PeopleControllerIndexTest#test_should_get_previously_on_show:
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR: column people.vote_count does not exist
LINE 1: ...s"."show_id" = $1 GROUP BY "people"."id" ORDER BY people.vot...
^
If I dump the SQL using #people.to_sql, this is what I get:
SELECT people.*, COUNT(nullif(votes.fulfilled, true)) AS people.vote_count FROM "people" LEFT OUTER JOIN "votes" ON "votes"."person_id" = "people"."id" GROUP BY "people"."id" ORDER BY people.vote_count DESC
Why is this failing on Postgres but working on SQLite? And what should I be doing instead to make it work on Postgres?
(PS: I named the field people.vote_count, with a dot, so I can access it in my view without having to do another SQL query to actually view the vote count for each person in the view (not sure if this works) but I get the same error even if I name the field simply vote_count.)
(PS2: I recently added the .uniq!(:group) because of some deprecation warning for Rails 6.2, but I couldn't find any documentation for it so I am not sure I am doing it right, still the error is there without that part.)
Are you sure you're not getting a syntax error from PostgreSQL somewhere? If you do something like this:
select count(*) as t.vote_count from t ... order by t.vote_count
I get a syntax error before PostgreSQL gets to complain about there being no t.vote_count column.
No matter, the solution is to not try to put your vote_count in the people table:
people = people.select("people.*, COUNT(#{count}) AS vote_count")
...
people.order(vote_count: :desc)
You don't need it there, you'll still be able to reference the vote_count just like any "normal" column in people. Anything in the select list will appear as an accessor in the resultant model instances whether they're columns or not, they won't show up in the #inspect output (since that's generated based on the table's columns) but you call the accessor methods nonetheless.
Historically there have been quite a few AR problems (and bugs) in getting the right count by just using count on a scope, and I am not sure they are actually all gone.
That depends on the scope (AR version, relations, group, sort, uniq, etc). A defaut count call that a gem has to generically use on a scope is not a one-fit-all solution. For that known reason Pagy allows you to pass the right count to its pagy method as explained in the Pagy documentation.
Your scope might become complex and the default pagy collection.count(:all) may not get the actual count. In that case you can get the right count with some custom statement, and pass it to pagy.
#pagy, #records = pagy(collection, count: your_count)
Notice: pagy will efficiently skip its internal count query and will just use the passed :count variable.
So... just get your own calculated count and pass it to pagy, and it will not even try to use the default.
EDIT: I forgot to mention: you may want to try the pagy arel extra that:
adds specialized pagination for collections from sql databases with GROUP BY clauses, by computing the total number of results with COUNT(*) OVER ().
Thanks to all the comments and answers I have finally found a solution which I think is the best way to solve this.
First of, the issue occurred when I called pagy which tried to count my scope by appending .count(:all). This is what caused the errors. The solution was to not create a "field" in select() and use it in .order().
So here is the proper code:
def self.order_by_votes(show = nil)
count = if show
"case when votes.show_id = #{show.id} AND NOT votes.fulfilled then 1 else null end"
else
'nullif(votes.fulfilled, true)'
end
left_joins(:votes).group(:id)
.uniq!(:group)
.select("people.*, COUNT(#{count}) as vote_count")
.order(Arel.sql("COUNT(#{count}) DESC"))
end
This sorts the number of people on the number of unfulfilled votes for them, with the ability to count only votes for a given show, and it works with pagy(), and pagy_arel() which in my case is a much better fit, so the results can be properly paginated.
I have updated this question
I have the following SQL scope in a RAILS 4 app, it works, but has a couple of issues.
1) Its really RAW SQL and not the rails way
2) The string interpolation opens up risks with SQL injection
here is what I have:
scope :not_complete -> (user_id) { joins("WHERE id NOT IN
(SELECT modyule_id FROM completions WHERE user_id = #{user_id})")}
The relationship is many to many, using a join table called completions for matching id(s) on relationships between users and modyules.
any help with making this Rails(y) and how to set this up to take the arg of user_id with out the risk, so I can call it like:
Modyule.not_complete("1")
Thanks!
You should have added few info about the models and their assocciation, anyways here's my trial, might have some errors because I don't know if the assocciation is one to many or many to many.
scope :not_complete, lambda do |user_id|
joins(:completion).where.not( # or :completions ?
id: Completion.where(user_id: user_id).pluck(modyule_id)
)
end
PS: I turned it into multi line just for readability, you can change it back to a oneline if you like.
I have a field in the XML file, categ_id. I need to access the value of that field in my Python code, in product_template class. I tried vals as a paremeter but it did not work.
If you can give me an example object.field_name as it relates to the case I have described.
Nebojsa - your question is not understandable at all, but I'll try to answer it. You can get the value of categ_id in two or even three ways:
vals.get('categ_id') - this is the way to go when you are creating a new record or updating existing one with change in categ_id field - otherwise you'll get an error or NoneType defined.
template = self.pool.get('product.template).browse(cr, uid, ids) and then template.categ_id.id - to get the value when you do have an id of the record, so you can ask database of value stored or in transaction, if there were any changes.
third opition is the dirtiest one, because it is just cr.execute("SELECT categ_id FROM product_template WHERE id = %s", (ids[0],)) and then category_id = cr.fetchall() - it is not always good option to use that, as it asks for records already existing in database (not counting these in transaction)
I have a table KmRelationship which associates Keywords and Movies
In keyword index I would like to list all keywords that appear most frequently in the KmRelationships table and only take(20)
.order doesn't seem to work no matter how I use it and where I put it and same for sort_by
It sounds relatively straight forward but i just can't seem to get it to work
Any ideas?
Assuming your KmRelationship table has keyword_id:
top_keywords = KmRelationship.select('keyword_id, count(keyword_id) as frequency').
order('frequency desc').
group('keyword_id').
take(20)
This may not look right in your console output, but that's because rails doesn't build out an object attribute for the calculated frequency column.
You can see the results like this:
top_keywords.each {|k| puts "#{k.keyword_id} : #{k.freqency}" }
To put this to good use, you can then map out your actual Keyword objects:
class Keyword < ActiveRecord::Base
# other stuff
def self.most_popular
KmRelationship.
select('keyword_id, count(keyword_id) as frequency').
order('frequency desc').
group('keyword_id').
take(20).
map(&:keyword)
end
end
And call with:
Keyword.most_popular
#posts = Post.select([:id, :title]).order("created_at desc").limit(6)
I have this listed in my controller index method which allows the the order to show the last post with a limit of 6. It might be something similar to what you are trying to do. This code actually reflects a most recent post on my home page.
I have been struggling with this, i have two models and showing data in Cgridview with one model, this model contains some id's whose values are in different table
So, i have added
'value'=> 'TblAreaoflaw::model()->FindByPk($data->typeoflaw)->areaoflaw'
which is giving this error
"Trying to get property of non-object"
Might be due to this reason that the some records doesn't exist in the TblAreaoflaw. Can't we check in this line through isset?
When i put static value, it work well, like
'value'=> 'TblAreaoflaw::model()->FindByPk(5)->areaoflaw',
Could anyone please help
thanks a lot
The error you get is because this expression TblAreaoflaw::model()->FindByPk($data->typeoflaw) is returning null. This means that you are effectively trying to get null->areaoflaw which won't work (this is what the error message "Trying to get property of non-object" clarifies).
My best guess is that $data->typeoflaw returns a non-existing primary key for the TblAreaoflaw model.
Make sure :
TblAreaoflaw is actually a model, I doubt its Areaoflaw
You have database specified primary key which is the id (5) you are passing
Try:
'value'=> '(TblAreaoflaw::model()->FindByPk($data->typeoflaw)->areaoflaw) ?
: "default or null value"'
Obviously substitute the null string to whatever you want. You may need to adjust the condition to use !empty() or similar, but see how it goes. (And if you do that or aren't using PHP 5.3, use the full ternary expression.)