How to divide a bigdecimal object coming from OCI8 recordset?

Question

def main()

  myDB=DB.new('myUser','myPass','myDB')
  record = myDB.handle().select_one('select count(*) from things')
  printf "%10d" % record

end

main() result: 30008428

I want to divide this value by 24 to create batches which will be executed every hour. This is the pretty print result:

[#<BigDecimal:ac2fdf94,'0.30008428E8',8(12)>]

I'm pretty confused on how to achieve that. As I understand it "record" is an array with a BigDecimal object in it. I tried to do record[0].div(24) that didn't work either. record.div(24) also didn't work.

Since I've spent quite a bit of time figuring it out now, I feel like I need to turn to the community for a little bit of help.

Thanks in advance.

Answer 1

The DBI::Handle#select_one method (which I imagine is what must be hidden behind your DB module) returns a single record from the database. Because this one record could potentially contain several fields, it returns the record as an array. In this case there is only a single column - the count - so that count value is in record[0].

I guess by "pretty print" you mean the output from p record, which is debugging output rather than just pretty printing. It is the equivalent of puts record.inspect. In this case it shows a single object (everything within #<...>) inside an array (the [...]).

In the case of BigDecimal objects, inspect returns a string giving the class name, BigDecimal; the address in hex, ac2fdf94; the current value as a string, 0.30008428E8; and the current (maximum) number of significant figures, 8 (12).

The short answer to your question is that you probably want to write

count = record[0].to_i

and use count thereafter, which is a normal Fixnum, so your division looks like

per_hour = count / 24.0

A value of 30,008,428 is well within the maximum Fixnum value, which depends on your machine word size but is probably 2³⁰ or over one billion. And even if you exceed that value, Ruby will - mostly silently - convert to a Bignum for you so nothing bad should happen.