Is it possible in Rails, to create an "empty" ActiveRecord Query object for a given model? Empty means for me a condition, that includes all possible rows in the db. I want to apply filters to that query afterwards.
At the moment I am using Booking.where('id > ?', 0), but I believe there has to be a nicer way like Booking.all() - but all() returns an array and not an ActiveRecord. Here´s my code:
#bookings = Booking.where('id > ?', 0)
if !#day.nil?
#bookings = #bookings.where('day = ?',#day)
end
if #project_id && !#project_id.empty?
#bookings = #bookings.where('project_id = ?', #project_id)
end
Thanks for your help!
You can use the scoped method discussed here: http://guides.rubyonrails.org/active_record_querying.html#working-with-scopes
Also note that #project_id.present? is the same as
#project_id && !#project_id.empty?
Use unscoped to create an empty query so you can build on it. (scoped is deprecated).
#bookings = Booking.unscoped
if !#day.nil?
#bookings = #bookings.where('day = ?',#day)
end
if #project_id && !#project_id.empty?
#bookings = #bookings.where('project_id = ?', #project_id)
end
(BTW in the absence of this you could also initialise it with Booking.where(true) instead of the id > 0 check; it's cleaner and likely to perform be better than doing a real condition check. But, unscoped is better still.)
Related
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
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 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
I've got myself in a bit of a pickle!
I've done a snazzy LINQ statement that does the job in my web app, but now I'd like to use this in a stored procedure:
var r = (from p in getautocompleteweightsproducts.tblWeights
where p.MemberId == memberid &&
p.LocationId == locationid
select p);
if (level != "0")
r = r.Where(p => p.MaterialLevel == level);
if (column == "UnitUserField1")
r = r.Where(p => p.UnitUserField1 == acitem);
if (column == "UnitUserField2")
r = r.Where(p => p.UnitUserField2 == acitem);
return r.OrderBy(p => p.LevelNo).ToList();
However, I can't for the life of me get the conditional where clause to work!!
If someone can point me in the right direction, I'd be most grateful.
Kind regards
Maybe something like this?
SELECT *
FROM dbo.weights
WHERE member_id = #memberid
AND location_id = #locationid
AND material_level = CASE WHEN #level = '0' THEN material_level
ELSE #level END
AND #acitem = CASE #column WHEN 'UnitUserField1' THEN unit_user_field_1
WHEN 'UnitUserField2' THEN unit_user_field_2
ELSE #acitem END
ORDER BY level_no
Have you tried LinqPAD, I'm pretty sure last time I played with that you could enter "LINQ to SQL" code and see the resulting SQL that produced. Failing that, place a SQL trace/profiler on your code running the LinqTOSQL and find the query being executed in the trace.
LukeH's answer will give you the correct rows, but there is something lost when you try to replace a query-generating-machine with a single query. There are parts of that query that are opaque to the optimizer.
If you need the original queries as-would-have-been-generated-by-linq, there are two options.
Generate every possible query and control which one runs by IF ELSE.
Use Dynamic sql to construct each query (although this trades away many of the benefits of using a stored procedure).
If you do decide to use dynamic sql, you should be aware of the curse and blessings of it.