Creating an array of hashes using find_each

Question

I am trying to create an array of hashes. I was able to create one using User.all but I don't want to load all the data at once, so I am trying to use find_each. I am new to ruby can someone point out what I am doing wrong ?

When I use .all

2.0.0 (main):0 > User.all.as_json.map { |u| {
2.0.0 (main):0 * index: {id: u["user"]["id"]}}}
[{:index=>{:id=>443}},
 {:index=>{:id=>3642}},
 {:index=>{:id=>506}}, ...

When I use find_each

2.0.0 (main):0 > User.find_each { |u|
2.0.0 (main):0 *   u = u.to_json;
2.0.0 (main):0 *   u = JSON.parse(u);
2.0.0 (main):0 * {index: { id: u["user"]["id"]}}}
  User Load (19.2ms)  SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT 1000
  User Load (18.2ms)  SELECT "users".* FROM "users" WHERE ("users"."id" > 1038) ORDER BY "users"."id" ASC LIMIT 1000
  User Load (21.4ms)  SELECT "users".* FROM "users" WHERE ("users"."id" > 2105) ORDER BY "users"."id" ASC LIMIT 1000
  User Load (14.5ms)  SELECT "users".* FROM "users" WHERE ("users"."id" > 3139) ORDER BY "users"."id" ASC LIMIT 1000
=> nil

Here's an answer that'll get you most of the way there, might be some messing about with the json. — Mike H-R
– Mike H-R, Commented Apr 16, 2014 at 18:08
I was curious to know, why you were doing first to_json than JSON.parse?? — Saurabh
– Saurabh, Commented Apr 16, 2014 at 18:11
don't you need to convert it into JSON then parse it to access the data inside ? — yesh
– yesh, Commented Apr 16, 2014 at 18:21

Arup Rakshit · Accepted Answer · 2014-04-16 19:22:10Z

2

find_each doesn't return anything, it just passes it into the block given.

my_objects = []
User.find_each { |u|
  u = u.to_json
  u = JSON.parse(u)
  my_objects << {index: { id: u["user"]["id"]}}
}
my_objects.to_json

See the docs for more info on find each and it's usage (such as batch_size, e.t.c.).

edited Apr 16, 2014 at 19:22

Arup Rakshit

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answered Apr 16, 2014 at 18:07

Mike H-R

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