refactor this ruby database/sequel gem lookup - ruby

Question

I know this code is not optimal, any ideas on how to improve it?
job_and_cost_code_found = false
timberline_db['SELECT Job, Cost_Code FROM [JCM_MASTER__COST_CODE] WHERE [Job] = ? AND [Cost_Code] = ?', job, clean_cost_code].each do |row|
job_and_cost_code_found = true
end
if job_and_cost_code_found == false then
info = linenum + "," + id + ",,Employees default job and cost code do not exist in timberline. job:#{job} cost code:#{clean_cost_code}"
add_to_exception_output_file(info)
end

Answer 1

You're breaking a lot of simple rules here.
Don't select what you don't use.
You select a number of columns, then completely ignore the result data. What you probably want is a count:
SELECT COUNT(*) AS cost_code_count FROM [JCM_MASTER__COST_CODE] WHERE [Job] = ? AND [Cost_Code] = ?'
Then you'll get one row that will have either a zero or non-zero value in it. Save this into a variable like:
job_and_cost_codes_found = timberline_db[...][0]['cost_code_count']
Don't compare against false unless you need to differentiate between that and nil
In Ruby only two things evaluate as false, nil and false. Most of the time you will not be concerned about the difference. On rare occasions you might want to have different logic for set true, set false or not set (nil), and only then would you test so specifically.
However, keep in mind that 0 is not a false value, so you will need to compare against that.
Taking into account the previous optimization, your if could be:
if job_and_cost_codes_found == 0
# ...
end
Don't use then or other bits of redundant syntax
Most Ruby style-guides spurn useless syntax like then, just as they recommend avoiding for and instead use the Enumerable class which is far more flexible.
Manipulate data, not strings
You're assembling some kind of CSV-like line in the end there. Ideally you'd be using the built-in CSV library to do the correct encoding, and libraries like that want data, not a string they'd have to parse.
One step closer to that is this:
line = [
linenum,
id,
nil,
"Employees default job and cost code do not exist in timberline. job:#{job} cost code:#{clean_cost_code}"
].join(',')
add_to_exception_output_file(line)
You'd presumably replace join(',') with the proper CSV encoding method that applies here. The library is more efficient when you can compile all of the data ahead of time into an array-of-arrays, so I'd recommend doing that if this is the end goal.
For example:
lines = [ ]
# ...
if (...)
# Append an array to the lines to write to the CSV file.
lines << [ ... ]
end
Keep your data in a standard structure like an Array, a Hash, or a custom object, until you're prepared to commit it to its final formatted or encoded form. That way you can perform additional operations on it if you need to do things like filtering.

Answer 2

It's hard to refactor this when I'm not exactly sure what it's supposed to be doing, but assuming that you want to log an error when there's no entry matching a job & code pair, here's what I've come up with:
def fetch_by_job_and_cost_code(job, cost_code)
timberline_db['SELECT Job, Cost_Code FROM [JCM_MASTER__COST_CODE] WHERE [Job] = ? AND [Cost_Code] = ?', job, cost_code]
end
if fetch_by_job_and_cost_code(job, clean_cost_code).none?
add_to_exception_output_file "#{linenum},#{id},,Employees default job and cost code do not exist in timberline. job:#{job} cost code:#{clean_cost_code}"
end