Ruby script with mysql2 gem - compare db date to Date.new

Question

I am writing a Ruby script which uses the mysql2 gem and runs under apache2/passenger.It does not use rails.

The script iterates through a mySql query result and compares a database date to today to get the elapsed time in days. The problem is that the resultant string from subtracting a database date from Date.new is a string like -2457521/1. The correct answer should be 0.

I have tried converting the date to a Ruby date with Date.parse() and Date.strptime() but get the same result. How can I subtract these dates to get the number of days between them?

Here is a redacted code extract from my script.

require 'mysql2'

class Uptime

  def call(env)

    results = con.query("SELECT * FROM Uptimes ORDER BY Up DESC LIMIT 10")

    flag = 0

    results.each(symbolize_keys: true) do |row| 

       if flag == 0 
          last_event = row[:Up]  # => 2016-05-12
          flag = 1
       end

    end  

#        last_event = Date.parse("#{last_event}")

#        last_event = Date.strptime("#{last_event}" "%Y-%m-%d") 

         days = Date.new - last_event # => -2457521/1


        [200, {"Content-Type" => "text/html"}, [html]]
  end
end

Akshay Pardhanani · Accepted Answer · 2016-05-12 11:01:41Z

1

I think your problem is the fact that you are using Date.new when I run Date.new in irb it returns the following:

#<Date: -4712-01-01 ((0j,0s,0n),+0s,2299161j)>

That looks like a 1st January of some year.

If you use Date.today instead that will return the current date to you.

I get this when I run that in irb #<Date: 2016-05-12 ((2457521j,0s,0n),+0s,2299161j)> notice 2016-05-12 vs -4712-01-01 this is also the reason why your result is negative.

Hope this answer helps :)

answered May 12, 2016 at 11:01

Akshay Pardhanani

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4 Comments

markhorrocks Over a year ago

That's close but Date.today - last_event returns 0/1

Akshay Pardhanani Over a year ago

Please can you tell me what is the result of running last_event.class? I notice you have commented out Date.parse("#{last_event}") maybe last_event is not of the Date class when you are subtracting it from Date.today

markhorrocks Over a year ago

I have previously checked class and found them to be both Date. Anyway, (Date.today - last_event).to_i gives me the right result so I will mark your answer correct, thanks.

Akshay Pardhanani Over a year ago

Glad I could help :) and thank you for accepting my answer

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