I am using active record to create array.
users = User.all.to_a
now I want to later on find with in this array user id: 1
users.find(1)
but it is not giving result but returning everything. How can I search in this result array my selected user id. I can see users is a an array but with in array each record of User object.
If I do following
user.first
it return User object, but I want to search, how can I do it. I understand if I remove to_a then it will work but then it will create another sql query.
Since it is an array of objects, you should use find with block:
users.find { |user| user.id == 1 }
User.find(1) is an ActiveRecord::FinderMethod. But when you already loaded all records into memory then those records are transformed into instances of User and stored in an Array. Therefore you need to use find or select which are implemented on Array like this:
users.find { |user| user.id == 1 } #=> returns the first found record
users.select { |user| user.id == 1 } #=> returns an array with all found record
Keep in mind that database queries are able to use efficient indexes when properly set up. Which makes database queries very fast. When you load all records into memory then those records need to be translated into proper instances. And searching on an array cannot use any index which means it could be (depending on the size of the array) slower than a new database query.
Related
I need to compare the 2 arrays declared here to return records that exist only in the filtered_apps array. I am using the contents of previous_apps array to see if an ID in the record exists in filtered_apps array. I will be outputting the results to a CSV and displaying records that exist in both arrays to the console.
My question is this: How do I get the records that only exist in filtered_apps? Easiest for me would be to put those unique records into a new array to work with on the csv.
start_date = Date.parse("2022-02-05")
end_date = Date.parse("2022-05-17")
valid_year = start_date.year
dupe_apps = []
uniq_apps = []
# Finding applications that meet my criteria:
filtered_apps = FinancialAssistance::Application.where(
:is_requesting_info_in_mail => true,
:aasm_state => "determined",
:submitted_at => {
"$exists" => true,
"$gte" => start_date,
"$lte" => end_date })
# Finding applications that I want to compare against filtered_apps
previous_apps = FinancialAssistance::Application.where(
is_requesting_info_in_mail: true,
:submitted_at => {
"$exists" => true,
"$gte" => valid_year })
# I'm using this to pull the ID that I'm using for comparison just to make the comparison lighter by only storing the family_id
previous_apps.each do |y|
previous_apps_array << y.family_id
end
# This is where I'm doing my comparison and it is not working.
filtered_apps.each do |app|
if app.family_id.in?(previous_apps_array) == false
then #non_dupe_apps << app
else "No duplicate found for application #{app.hbx_id}"
end
end
end
So what am I doing wrong in the last code section?
Let's check your original method first (I fixed the indentation to make it clearer). There's quite a few issues with it:
filtered_apps.each do |app|
if app.family_id.in?(previous_apps_array) == false
# Where is "#non_dupe_apps" declared? It isn't anywhere in your example...
# Also, "then" is not necessary unless you want a one-line if-statement
then #non_dupe_apps << app
# This doesn't do anything, it's just a string
# You need to use "p" or "puts" to output something to the console
# Note that the "else" is also only triggered when duplicates WERE found...
else "No duplicate found for application #{app.hbx_id}"
end # Extra "end" here, this will mess things up
end
end
Also, you haven't declared previous_apps_array anywhere in your example, you just start adding to it out of nowhere.
Getting the difference between 2 arrays is dead easy in Ruby: just use -!
uniq_apps = filtered_apps - previous_apps
You can also do this with ActiveRecord results, since they are just arrays of ActiveRecord objects. However, this doesn't help if you specifically need to compare results using the family_id column.
TIP: Getting the values of only a specific column/columns from your database is probably best done with the pluck or select method if you don't need to store any other data about those objects. With pluck, you only get an array of values in the result, not the full objects. select works a bit differently and returns ActiveRecord objects, but filters out everything but the selected columns. select is usually better in nested queries, since it doesn't trigger a separate query when used as a part of another query, while pluck always triggers one.
# Querying straight from the database
# This is what I would recommend, but it doesn't print the values of duplicates
uniq_apps = filtered_apps.where.not(family_id: previous_apps.select(:family_id))
I highly recommend getting really familiar with at least filter/select, and map out of the basic array methods. They make things like this way easier. The Ruby docs are a great place to learn about them and others. A very simple example of doing a similar thing to what you explained in your question with filter/select on 2 arrays would be something like this:
arr = [1, 2, 3]
full_arr = [1, 2, 3, 4, 5]
unique_numbers = full_arr.filter do |num|
if arr.include?(num)
puts "Duplicates were found for #{num}"
false
else
true
end
end
# Duplicates were found for 1
# Duplicates were found for 2
# Duplicates were found for 3
=> [4, 5]
NOTE: The OP is working with ruby 2.5.9, where filter is not yet available as an array method (it was introduced in 2.6.3). However, filter is just an alias for select, which can be found on earlier versions of Ruby, so they can be used interchangeably. Personally, I prefer using filter because, as seen above, select is already used in other methods, and filter is also the more common term in other programming languages I usually work with. Of course when both are available, it doesn't really matter which one you use, as long as you keep it consistent.
EDIT: My last answer did, in fact, not work.
Here is the code all nice and working.
It turns out the issue was that when comparing family_id from the set of records I forgot that the looped record was a part of the set, so it would return it, too. I added a check for the ID of the array to match the looped record and bob's your uncle.
I added the pass and reject arrays so I could check my work instead of downloading a csv every time. Leaving them in mostly because I'm scared to change anything else.
start_date = Date.parse(date_from)
end_date = Date.parse(date_to)
valid_year = start_date.year
date_range = (start_date)..(end_date)
comparison_apps = FinancialAssistance::Application.by_year(start_date.year).where(
aasm_state:'determined',
is_requesting_voter_registration_application_in_mail:true)
apps = FinancialAssistance::Application.where(
:is_requesting_voter_registration_application_in_mail => true,
:submitted_at => date_range).uniq{ |n| n.family_id}
#pass_array = []
#reject_array = []
apps.each do |app|
family = app.family
app_id = app.id
previous_apps = comparison_apps.where(family_id:family.id,:id.ne => app.id)
if previous_apps.count > 0
#reject_array << app
puts "\e[32mApplicant hbx id \e[31m#{app.primary_applicant.person_hbx_id}\e[32m in family ID \e[31m#{family.id}\e[32m has registered to vote in a previous application.\e[0m"
else
<csv fields here>
csv << [csv fields here]
end
end
Basically, I pulled the applications into the app variable array, then filtered them by the family_id field in each record.
I had to do this because the issue at the bottom of everything was that there were records present in app that were themselves duplicates, only submitted a few days apart. Since I went on the assumption that the initial app array would be all unique, I thought the duplicates that were included were due to the rest of the code not filtering correctly.
I then use the uniq_apps array to filter through and look for matches in uniq_apps.each do, and when it finds a duplicate, it adds it to the previous_applications array inside the loop. Since this array resets each go-round, if it ever has more than 0 records in it, the app gets called out as being submitted already. Otherwise, it goes to my csv report.
Thanks for the help on this, it really got my brain thinking in another direction that I needed to. It also helped improve the code even though the issue was at the very beginning.
So i have a small test collection that has this format...
Sample Data
I have created a simple query that returns an array with all the ids..
All_Ids = db.Test_Collection.find({}, {_id:1}).map(function(item){ return item._id; })
[ 98800754, 15301328, 76812898 ]
And i Want to take in an inputted id and check to see if that inputted value is present in the array..
here was my initial attempt..
> query_Figure = 98800754
98800754
> db.Test_Collection.find({query_Figure: {$in: All_Ids}})
I tried using the $in operator to find that specific value.. with the array and specific id to be searched as variables, but had no luck as the query returned nothing, when the value im searching for is clearly in the array
As you can tell I am a newbie and would appreciate some help in improving the query!
$in operator returns the documents in which value of the specified field is present in the array.
In your case, since query_Figure is not a field in any of your documents, your query returns no matching documents.
If you just want to check if the input id is present in the All_Ids array, then you don't need a query. Just use Array.prototype.includes()
const exists = All_Ids.includes(query_Figure);
After much googling and console testing I need some help with arrays in rails. In a method I do a search in the db for all rows matching a certain requirement and put them in a variable. Next I want to call each on that array and loop through it. My problem is that sometimes only one row is matched in the initial search and .each causes a nomethoderror.
I called class on both situations, where there are multiple rows and only one row. When there are multiple rows the variable I dump them into is of the class array. If there is only one row, it is the class of the model.
How can I have an each loop that won't break when there's only one instance of an object in my search? I could hack something together with lots of conditional code, but I feel like I'm not seeing something really simple here.
Thanks!
Requested Code Below
#user = User.new(params[:user])
if #user.save
#scan the invites dbtable and if user email is present, add the new uid to the table
#talentInvites = TalentInvitation.find_by_email(#user.email)
unless #talentInvites.nil?
#talentInvites.each do |tiv|
tiv.update_attribute(:user_id, #user.id)
end
end
....more code...
Use find_all_by_email, it will always return an array, even empty.
#user = User.new(params[:user])
if #user.save
#scan the invites dbtable and if user email is present, add the new uid to the table
#talentInvites = TalentInvitation.find_all_by_email(#user.email)
unless #talentInvites.empty?
#talentInvites.each do |tiv|
tiv.update_attribute(:user_id, #user.id)
end
end
I have a table called devicesegments, each row of which contains a large array called devices. Owing to the size of the device array, I've been asked not to include it in my query for a page that lists all devicesegments, but only include their count. Is this possible?
What I was doing before :
A simple db.devicesegments.find()
What I'm doing now :
db.devicesegments.find({}, { devices : 0 })
What I want to achieve :
db.devicesegments.find({}, { devices : 0, devices.length : 1 })
Something like a COUNT(devices) AS device_count!
Ashkay, there's no way to do this with Mongo currently. As #rompetroll says, your application should keep a "count" field on each document, and carefully $inc it whenever you change the number of entries in the array. Then when you query for the document, exclude the array like:
db.collection.find({}, {devices:0})
If you're willing to run MongoDB 2.1, which is a development release, the aggregation framework provides a means to calculate the array size within a query:
http://www.mongodb.org/display/DOCS/Aggregation+Framework
Since there is no way to currently do this, without including a new device_count in my table, the temporary fix that I applied was to fetch all the data from the database, along with the devices array, and for each row, add a field for devices.length and then remove the devices array before sending the data across.
I have a set of entries in the datastore and I would like to search/retrieve them as user types query. If I have full string it's easy:
q := datastore.NewQuery("Products").Filter("Name =", name).Limit(20)
but I have no idea how to do it with partial string, please help.
q := datastore.NewQuery("Products").Filter("Name >", name).Limit(20)
There is no like operation on app engine but instead you can use '<' and '>'
example:
'moguz' > 'moguzalp'
EDIT: GAH! I just realized that your question is Go-specific. My code below is for Python. Apologies. I'm also familiar with the Go runtime, and I can work on translating to Python to Go later on. However, if the principles described are enough to get you moving in the right direction, let me know and I wont' bother.
Such an operation is not directly supported on the AppEngine datastore, so you'll have to roll your own functionality to meet this need. Here's a quick, off-the-top-of-my-head possible solution:
class StringIndex(db.Model):
matches = db.StringListProperty()
#classmathod
def GetMatchesFor(cls, query):
found_index = cls.get_by_key_name(query[:3])
if found_index is not None:
if query in found_index.matches:
# Since we only query on the first the characters,
# we have to roll through the result set to find all
# of the strings that matach query. We keep the
# list sorted, so this is not hard.
all_matches = []
looking_at = found_index.matches.index(query)
matches_len = len(foundIndex.matches)
while start_at < matches_len and found_index.matches[looking_at].startswith(query):
all_matches.append(found_index.matches[looking_at])
looking_at += 1
return all_matches
return None
#classmethod
def AddMatch(cls, match) {
# We index off of the first 3 characters only
index_key = match[:3]
index = cls.get_or_insert(index_key, list(match))
if match not in index.matches:
# The index entity was not newly created, so
# we will have to add the match and save the entity.
index.matches.append(match).sort()
index.put()
To use this model, you would need to call the AddMatch method every time that you add an entity that would potentially be searched on. In your example, you have a Product model and users will be searching on it's Name. In your Product class, you might have a method AddNewProduct that creates a new entity and puts it into the datastore. You would add to that method StringIndex.AddMatch(new_product_name).
Then, in your request handler that gets called from your AJAXy search box, you would use StringIndex.GetMatchesFor(name) to see all of the stored products that begin with the string in name, and you return those values as JSON or whatever.
What's happening inside the code is that the first three characters of the name are used for the key_name of an entity that contains a list of strings, all of the stored names that begin with those three characters. Using three (as opposed to some other number) is absolutely arbitrary. The correct number for your system is dependent on the amount of data that you are indexing. There is a limit to the number of strings that can be stored in a StringListProperty, but you also want to balance the number of StringIndex entities that are in your datastore. A little bit of math with give you a reasonable number of characters to work with.
If the number of keywords is limited you could consider adding an indexed list property of partial search strings.
Note that you are limited to 5000 indexes per entity, and 1MB for the total entity size.
But you could also wait for Cloud SQL and Full Text Search API to be avaiable for the Go runtime.