I have a database with a field that is a "pseudo" array. This array holds integer values. My implementation is as follows:
attendees = models.TextField(null=True) # declaring the integer array
When I say pseudo, I mean that I am using json to make it into an array.
attendees=json.dumps(members)
Now the attendees column will contain something like this ["1", "2", "3"]
So I want to check if attendees will contain the value "1" for example. Essentially, I want something like this:
eventList = Events.objects.all().filter(user_id in Event.attendees) # I know this isn't the correct syntax
Any ideas on how to do this as efficiently as possible?
You'll need to use __contains
.filter(attendees__contains='"{}"'.format(user_id))
Although the question remains why this isn't a separate model or JSONField/ArrayField...
Related
I would like to check whether certain values are contained at a certain index in the array.
With the following statement I can check whether "Value1" is contained at position "1":
'''$myArray.get(1).contains('value1')'''
What if I want to check at position "1" whether "Value1" or "Value2" are included (or more than two).
I would like to avoid creating multiple conditions with OR links in the Watson Assistant Node.
If you don't want to create multiple conditions you can use regex.
String[] myArray = {"Value1", "Value2", "Value3"};
myArray[1].matches("(Value1|Value2|Value3)"); <-- will return true
You can basically add as much values as you want as a parameter to the matches() function.
So in the end your SpEL expression should look something like this:
"#myArray[1].matches('(Value1|Value2|Value3)')"
I have an object Persons which is an ActiveRecord model with some fields like :name, :age .etc.
Person has a 1:1 relationship with something called Account where every person has an account .
I have some code that does :
Account.create!(person: current_person)
where current_person is a specified existing Person active record object.
Note : The table Account has a field for person_id
and both of them have has_one in the model for each other.
Now I believe we could do something like below for bulk creation :
Account.create!([{person: person3},{person:: person2} ....])
I have an array of persons but am not sure of the best way to convert to an array of hashes all having the same key.
Basically the reverse of Convert array of hashes to array is what I want to do.
Why not just loop over your array of objects?
[person1, person2].each{|person| Account.create!(person: person)}
But if for any reason any of the items you loop over fail Account.create! you may be left in a bad state, so you may want to wrap this in an Active Record Transaction.
ActiveRecord::Base.transaction do
[person1, person2].each{|person| Account.create!(person: person)}
end
The create method actually persists each hash individually, as shown in the source code, so probably it's not what you are looking for. Either way the following code would do the job:
Account.create!(persons.map { |person| Hash[:person_id, person.id] })
If you need to create all records in the same database operation and are using rails 6+ you could use the insert_all method.
Account.insert_all(persons.map { |person| Hash[:person_id, person.id] })
For previous versions of rails you should consider using activerecord-import gem.
# Combination(1).to_a converts [1, 2, 3] to [[1], [2], [3]]
Account.import [:person_id], persons.pluck(:id).combination(1).to_a
I've been pulling data from an API in JSON, and am currently stumbling over an elmementary problem
The data is on companies, like Google and Facebook, and is in an array or hashes, like so:
[
{"id"=>"1", "properties"=>{"name"=>"Google", "stock_symbol"=>GOOG, "primary_role"=>"company"}},
{"id"=>"2", "properties"=>{"name"=>"Facebook", "stock_symbol"=>FB, "primary_role"=>"company"}}
]
Below are two operations I'd like to try:
For each company, print out the name, ID, and the stock symbol (i.e. "Google - 1 - GOOG" and "Facebook - 2 - FB")
Remove "primary role" key/value from Google and Facebook
Assign a new "industry" key/value for Google and Facebook
Any ideas?
Am a beginner in Ruby, but running into issues with some functions / methods (e.g. undefined method) for arrays and hashes as this looks to be an array OF hashes
Thank you!
Ruby provides a couple of tools to help us comprehend arrays, hashes, and nested mixtures of both.
Assuming your data looks like this (I've added quotes around GOOG and FB):
data = [
{"id"=>"1", "properties"=>{"name"=>"Google", "stock_symbol"=>"GOOG", "primary_role"=>"company"}},
{"id"=>"2", "properties"=>{"name"=>"Facebook", "stock_symbol"=>"FB", "primary_role"=>"company"}}
]
You can iterate over the array using each, e.g.:
data.each do |result|
puts result["id"]
end
Digging into a hash and printing the result can be done in a couple of ways:
data.each do |result|
# method 1
puts result["properties"]["name"]
# method 2
puts result.dig("properties", "name")
end
Method #1 uses the hash[key] syntax, and because the first hash value is another hash, it can be chained to get the result you're after. The drawback of this approach is that if you have a missing properties key on one of your results, you'll get an error.
Method #2 uses dig, which accepts the nested keys as arguments (in order). It'll dig down into the nested hashes and pull out the value, but if any step is missing, it will return nil which can be a bit safer if you're handling data from an external source
Removing elements from a hash
Your second question is a little more involved. You've got two options:
Remove the primary_role keys from the nested hashes, or
Create a new object which contains all the data except the primary_role keys.
I'd generally go for the latter, and recommend reading up on immutability and immutable data structures.
However, to achieve [1] you can do an in-place delete of the key:
data.each do |company|
company["properties"].delete("primary_role")
end
Adding elements to a hash
You assign new hash values simply with hash[key] = value, so you can set the industry with something like:
data.each do |company|
company["properties"]["industry"] = "Advertising/Privacy Invasion"
end
which would leave you with something like:
[
{
"id"=>"1",
"properties"=>{
"name"=>"Google",
"stock_symbol"=>"GOOG",
"industry"=>"Advertising/Privacy Invasion"
}
},
{
"id"=>"2",
"properties"=>{
"name"=>"Facebook",
"stock_symbol"=>"FB",
"industry"=>"Advertising/Privacy Invasion"
}
}
]
To achieve the first operation, you can iterate through the array of companies and access the relevant information for each company. Here's an example in Ruby:
companies = [ {"id"=>"1", "properties"=>{"name"=>"Google", "stock_symbol"=>"GOOG", "primary_role"=>"company"}}, {"id"=>"2", "properties"=>{"name"=>"Facebook", "stock_symbol"=>"FB", "primary_role"=>"company"}}]
companies.each do |company|
name = company['properties']['name']
id = company['id']
stock_symbol = company['properties']['stock_symbol']
puts "#{name} - #{id} - #{stock_symbol}"
end
This will print out the name, ID, and stock symbol for each company.
To remove the "primary role" key/value, you can use the delete method on the properties hash. For example:
companies.each do |company|
company['properties'].delete('primary_role')
end
To add a new "industry" key/value, you can use the []= operator to add a new key/value pair to the properties hash. For example:
companies.each do |company|
company['properties']['industry'] = 'Technology'
end
This will add a new key/value pair with the key "industry" and the value "Technology" to the properties hash for each company.
It's a good idea to save multiple addresses in a jsonb field in PostgreSQL. I'm new in nosql and I'd like to test PostgreSQL to do that. I don't want to have another table with addresses, I prefer to have it in the same table.
But I'm in doubt, I've seen PostreSQL have jsonb and jsonb[].
Which one is better to store multiple addresses?
If I use jsonb, I think I must to add a prefix for every field like this:
"1_adresse_line-1"
"1_adresse_line-2"
"1_postalcode"
"2_adresse_line-1"
"2_adresse_line-2"
"2_postalcode"
"3_adresse_line-1"
"3_adresse_line-2"
"3_postalcode"
etc.
Is it better to use jsonb[], how does it work?
Use a jsonb (not jsonb[]!) column with the structure like this:
select
'[{
"adresse_line-1": "a11",
"adresse_line-2": "a12",
"postalcode": "code1"
},
{
"adresse_line-1": "a21",
"adresse_line-2": "a22",
"postalcode": "code2"
}
]'::jsonb;
Though, a regular table related to the main one is a better option.
Why not jsonb[]? Take a look at JSON definition:
JSON is built on two structures:
A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array.
An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.
In a jsonb column you can therefore store an array of objects. Attempts to use the array of jsonb are probably due to misunderstanding of this type of data. I have never seen a reasonable need for such a solution.
I'm new to monogDB and trying to design the way I store my data so I can do the kinds of queries I want to. Say I have a document that looks like
{
"foo":["foo1","foo2","foo3"],
"bar":"baz"
}
Where the array "foo" is always of length 3, and the order of the items are meaningful. I would like to be able to make a query that searches for all documents where "foo2" == something. Essentially I want to treat "foo" like any old array and be able to index it in a search, so something like "foo"[1] == something.
Does monogDB support this? Would it be more correct to store my data like,
{
"foo":{
"foo1":"val1",
"foo2":"val2",
"foo3":"val3"
},
"bar":"baz"
}
instead? Thanks.
The schema you have asked about is fine.
To insert at a specific index of array:
Use the $position operator. Read here.
To query at a specific index location:
Use the syntax key.index. As in:
db.users.find({"foo.1":"foo2"})