I am trying to assign a variable tagcolor only if it already exists in the database. This code queries the DB twice if the color is present, once to determine if it does indeed exist and another to actually assign it.
If it doesn't exist I just want to assign tagcolor to the user provided color.
if Tagmap.where("name = ? AND user_id = ?", tag, current_user.id).first.present?
tagcolor = Tagmap.where("name = ? AND user_id = ?", tag, current_user.id).first.color
else
tagcolor = params[:color].downcase
end
Can I reduce this block so I just query the DB once?
Provided you're on Rails 4, you can do:
tagcolor = Tagmap.find_by(name: tag, user: current_user).try(:color) || params[:color].downcase
Similar (but not that pretty) construction is possible in Rails 3:
tagcolor = Tagmap.find_by_name_and_user(tag, current_user).try(:color) || params[:color].downcase
Related
I'm currently building a food application which has users select a range of options (perishable, non-perishable ) and (snack, produce or meal) via a set of radio buttons. I'm currently using node.js and sqlite 3 to query a database to determine which entries to return to the user after they search the database.
I want to write a query such that when the booleans from the client-side are sent over to the server, the server will choose the entries such that perishable if perishable is set to true on the client that the query will find just the perishable items and vice-versa. I also want the same functionality with
Example:
perishable = request.perishable.
non-perishable = request.non-perishable
snack = request.non-perishable
meal = request.non-perishable
produce = request.non-perishable.
var q = 'SELECT * FROM posts WHERE available == true AND (if perishable is true all rows where the perishable column is set to true... etc );
Why not just change the query based on perishable?
var q = 'SELECT * FROM posts WHERE available == true';
if (perishable)
q += ' AND perishable == true';
You can do it with a CASE WHEN syntax in WHERE:
WHERE perishable IS CASE WHEN [condition] THEN TRUE ELSE FALSE END
Just a quick tip. Search for this syntax in your database documentation.
I'd like to use something like find_in_batches, but instead of grouping fully instantiated AR objects, I would like to group a certain attribute, like, let's say, the id. So, basically, a mixture of using find_in_batches and pluck:
Cars.where(:engine => "Turbo").pluck(:id).find_in_batches do |ids|
puts ids
end
# [1, 2, 3....]
# ...
Is there a way to do this (maybe with Arel) without having to write the OFFSET/LIMIT logic myself or recurring to pagination gems like will paginate or kaminari?
This is not the ideal solution, but here's a method that just copy-pastes most of find_in_batches but yields a relation instead of an array of records (untested) - just monkey-patch it into Relation :
def in_batches( options = {} )
relation = self
unless arel.orders.blank? && arel.taken.blank?
ActiveRecord::Base.logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
end
if (finder_options = options.except(:start, :batch_size)).present?
raise "You can't specify an order, it's forced to be #{batch_order}" if options[:order].present?
raise "You can't specify a limit, it's forced to be the batch_size" if options[:limit].present?
relation = apply_finder_options(finder_options)
end
start = options.delete(:start)
batch_size = options.delete(:batch_size) || 1000
relation = relation.reorder(batch_order).limit(batch_size)
relation = start ? relation.where(table[primary_key].gteq(start)) : relation
while ( size = relation.size ) > 0
yield relation
break if size < batch_size
primary_key_offset = relation.last.id
if primary_key_offset
relation = relation.where(table[primary_key].gt(primary_key_offset))
else
raise "Primary key not included in the custom select clause"
end
end
end
With this, you should be able to do :
Cars.where(:engine => "Turbo").in_batches do |relation|
relation.pluck(:id)
end
this is not the best implementation possible (especially in regard to primary_key_offset calculation, which instantiates a record), but you get the spirit.
I'm trying to use .extra() where the query return more than 1 result, like :
'SELECT "books_books"."*" FROM "books_books" WHERE "books_books"."owner_id" = %s' % request.user.id
I got an error : only a single result allowed for a SELECT that is part of an expression
Try it on dev-server using sqlite3. Anybody knows how to fix this? Or my query is wrong?
EDIT:
I'm using django-simple-ratings, my model like this :
class Thread(models.Model):
#
#
ratings = Ratings()
I want to display each Thread's ratings and whether a user already rated it or not. For 2 items, it will hit 6 times, 1 for the actual Thread and 2 for accessing the ratings. The query:
threads = Thread.ratings.order_by_rating().filter(section = section)\
.select_related('creator')\
.prefetch_related('replies')
threads = threads.extra(select = dict(myratings = "SELECT SUM('section_threadrating'.'score') AS 'agg' FROM 'section_threadrating' WHERE 'section_threadrating'.'content_object_id' = 'section_thread'.'id' ",)
Then i can print each Thread's ratings without hitting the db more. For the 2nd query, i add :
#continue from extra
blahblah.extra(select = dict(myratings = '#####code above####',
voter_id = "SELECT 'section_threadrating'.'user_id' FROM 'section_threadrating' WHERE ('section_threadrating'.'content_object_id' = 'section_thread'.'id' AND 'section_threadrating'.'user_id' = '3') "))
Hard-coded the user_id. Then when i use it on template like this :
{% ifequal threads.voter_id user.id %}
#the rest of the code
I got an error : only a single result allowed for a SELECT that is part of an expression
Let me know if it's not clear enough.
The problem is in the query. Generally, when you are writing subqueries, they must return only 1 result. So a subquery like the one voter_id:
select ..., (select sectio_threadrating.user_id from ...) as voter_id from ....
is invalid, because it can return more than one result. If you are sure it will always return one result, you can use the max() or min() aggregation function:
blahblah.extra(select = dict(myratings = '#####code above####',
voter_id = "SELECT max('section_threadrating'.'user_id') FROM 'section_threadrating' WHERE ('section_threadrating'.'content_object_id' = 'section_thread'.'id' AND 'section_threadrating'.'user_id' = '3') "))
This will make the subquery always return 1 result.
Removing that hard-code, what user_id are you expecting to retrieve here? Maybe you just can't reduce to 1 user using only SQL.
I'm trying to select the following data with the limited information. The problem is that when I have added the .select distinct section it has killed my query.
#activities = Availability.select.("DISTINCT user_id").where("team_id = ? and schedule_id = ?", current_user[:team_id], #next_game).last(5)
There's one too many dot's in there as the 'DISTINCT user_id' is the arguments for the select method call.
So:
Availability.select("DISTINCT user_id").where("team_id = ? and schedule_id = ?", current_user[:team_id], #next_game).last(5)
Also be aware that you're now only selecting one attribute and you'll get a partial representation of the classes back. To circumvent this just select the attributes you need later in the code.
Availability.select("DISTINCT(`user_id`), `team_id`").where("team_id = ? and schedule_id = ?", current_user[:team_id], #next_game).last(5)
etc.
Hope this helps.
Im trying to build advanced search finder for my Candidate model.
Lets imagine it has couple fields + multiple associations like has_many: languages & has_many: skills. Now I'm building query like this:
query = Candidate.select("*")
if position_name
query = query.where('position_name LIKE ? OR position_name IS NULL',"%#{position_name}%")
end
if salary
query = query.where('salary <= ? OR salary IS NULL',salary)
end
and so on...
Now I want to add more advanced conditions like to find users who only have such skills like PHP and Java (so return only those users who have both skills)
This works but only when I insert OR
query = query.joins(:skills)
query = query.where('`skills`.`name` = ? OR `skills`.`name` = ?',"Java","PHP")
Additionally I'd like the same also for languages (plus, language have language.name & language.level)
Can someone points me in which direction to look? And also how to build such condition where I can multiple skills or multiple languages?
Have a look at the various search gems like Ransack, Metawhere or Searchlogic
http://rubygems.org/gems/ransack
https://github.com/railsdog/searchlogic
Both Ransack and Searchlogic allow searching on associated models and you can use scopes to restrict the search parameters.
Example Search params for Searchlogic.
[search][admitted_gte]
[search][admitted_lte]
[search][aetiology_like_any][] VIRUS
[search][at_risk_gte]
[search][at_risk_lte]
[search][died_gte]
[search][died_lte]
[search][gezi_reference_like]
[search][id]
[search][incidents_location_encrypted_postcode_like]
[search][lab_confirmed_gte]
[search][lab_confirmed_lte]
[search][onset_first_after]
[search][onset_first_before]
[search][onset_last_after]
[search][onset_last_before]
[search][outbreak_type_equals_any][] FOODBORNE
[search][point_source_date_after]
[search][point_source_date_before]
[search][total_affected_gte]
[search][total_affected_lte]
[search][user_reference_like]
[search][year_equals_any][] 2010
search[order] descend_by_id
Outbreak_Controller.rb Index action returns the results of the Search query. From 17 Search params only a single searchlogic call is required #search = Outbreak.search(params[:search]). The params are whitelisted against a list of allowed search params - code not shown.
def index
#set the default index order to be descending Outbreak id
if !params[:search][:order]
params[:search][:order] = "descend_by_id"
end
if params[:search][:bacterial_agents_bacterium_name_like_any] != nil && !params[:search][:bacterial_agents_bacterium_name_like_any].empty?
params[:search][:bacterial_agents_category_like] = "CAUSATIVE"
end
if params[:search][:viral_agents_virus_name_like_any] != nil && !params[:search][:viral_agents_virus_name_like_any].empty?
params[:search][:viral_agents_category_like] = "CAUSATIVE"
end
if params[:search][:protozoal_agents_protozoa_name_like_any] != nil && !params[:search][:protozoal_agents_protozoa_name_like_any].empty?
params[:search][:protozoal_agents_category_like] = "CAUSATIVE"
end
if params[:search][:toxic_agents_toxin_name_like_any] != nil && !params[:search][:toxic_agents_toxin_name_like_any].empty?
params[:search][:toxic_agents_category_like] = "CAUSATIVE"
end
#Outbreak.search takes all of the given params and runs it against the Outbreak model and it's associated models
#search = Outbreak.search(params[:search])
end