There might be an issue with the Kata's tests. I'm getting the following error after submission, although I don't have array + array operation.
The stack trace is:

An error occurred while loading ./spec/query_spec.rb.
Failure/Error: actual = DB[actual].to_a if actual.is_a?(String)

Sequel::DatabaseError:
  PG::UndefinedFunction: ERROR:  operator does not exist: integer[] + integer[]
  LINE 1: SELECT id, a, b, c, a + b AS "a + b", (a + b) + c AS "(a + b...
                                ^
  HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:156:in `exec'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:156:in `block in execute_query'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/database/logging.rb:38:in `log_connection_yield'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:156:in `execute_query'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:144:in `block in execute'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:120:in `check_disconnect_errors'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:144:in `execute'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:500:in `_execute'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:318:in `block (2 levels) in execute'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:522:in `check_database_errors'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:318:in `block in execute'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/connection_pool/threaded.rb:92:in `hold'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/database/connecting.rb:269:in `synchronize'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:318:in `execute'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/dataset/actions.rb:1093:in `execute'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:614:in `fetch_rows'
# /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/dataset/actions.rb:152:in `each'
# ./spec/support/preloaded.rb:11:in `to_a'
# ./spec/support/preloaded.rb:11:in `compare'
# ./spec/query_spec.rb:18:in `block in <top (required)>'
# ./spec/query_spec.rb:14:in `<top (required)>'
# ------------------
# --- Caused by: ---
# PG::UndefinedFunction:
#   ERROR:  operator does not exist: integer[] + integer[]
#   LINE 1: SELECT id, a, b, c, a + b AS "a + b", (a + b) + c AS "(a + b...
#                                 ^
#   HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
#   /usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:156:in `exec'
No examples found.

It seems for testing the column a + b AS "a + b" is used.

The description does not specify what a direction is. Only from the example can one assume that the directions are "up", "down", "left", "right", but this is not explicit.

Be careful with random tests for the final attempt, in my case sometimes they worked and sometimes not.
It should be better to have fixed tests that can be passed only by respecting certain conditions.

The description should clarify that:

• the id column is unique (reading the description, I first thought I had to GROUP BY id to collect the first and last ip each user connected from. This would make sense for a database that logs a triplet (user_id, user_ip, connection_time) each time a user connects to a server, as the description alludes to)
• the ip_address column is not a simple address, it is an address with a submask (denoted by a / character in the textual representation)

Solved this Kata in Python. Firstly wrote code in JS then translated it into Python. In JS it passed test cases for 1 - 10 roots, but failed for some '625-675 roots' cases. And it is impossible to debug it uses error message: expected 'x^673 - 2153x^672 + 1140664x^671 + 86…' to equal 'x^673 - 2153x^672 + 1140664x^671 + 86…' because in this message we can't undestand what is going wrong!!! More over the same Code translated to Python passed all tests! It is needed to do something with it!

Would be nice for a long test to provide some estimation of %% completion.
'''if(i%(BIG_SIZE/10)==0) printf("%2.0f of the Addition test passed\n",(double)i/BIG_SIZE);'''

That would give some clue if the solution is on the right track and need only cosmetical enhancments.

I think it would be much better if instead of writing about SQL magic, it would simply inform users about the creation of the operator.

I don't understand the task at all! Why in the sample table are 2 rows with the same user na same username. Example:
id = 1
user_id = 1
name = a

and few rows below

id = 3
user_id 1
name = a

Lovely kata! Just to clarify: the cost for passing a given coordinate will always be a natural number (i.e. an integer greater than 0), correct? (This is suggested by the formulation "moving to a neighboring coordinate counted not as 1 step but as N steps", but it could be stated more explicitly.)

Scala translation

Hey guys, can someone give me a hint on this one? I've been trying it for quite some time.
I'm using a BFS, but at this point I'm not quite sure if this is a good approach. A DFS would be any better?

Edit: scrolling down I saw my old post, from 6 months ago, hahah wow

I have a solutions that works using 'create function - unnest - ordinality - cardinality', but still I hece the same error:
I do not what is happening....any suggestion? Thks

--- Caused by: ---

PG::UndefinedFunction:

ERROR: operator does not exist: integer[] + integer[]

LINE 1: SELECT id, a, b, c, a + b AS "a + b", (a + b) + c AS "(a + b...

^

HINT: No operator matches the given name and argument types. You might need to add explicit type casts.

/usr/local/bundle/gems/sequel-5.47.0/lib/sequel/adapters/postgres.rb:156:in `exec'

No examples found.

I'm stuck at the monthly/yearly totals. I can get the daily totals, but dont know how to insert the others.