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I wrote a utility that helps find areas where you could optimize your program using a frozen string instead of a string literal, it's called [let_it_go](https://github.com/schneems/let_it_go). After going through the output and adding `.freeze` I was able to eliminate the creation of 1,114 string objects on EVERY request to [codetriage](codetriage.com). How does this impact execution?
To look at memory:
```ruby
require 'get_process_mem'
mem = GetProcessMem.new
GC.start
GC.disable
1_114.times { " " }
before = mem.mb
after = mem.mb
GC.enable
puts "Diff: #{after - before} mb"
```
Creating 1,114 string objects results in `Diff: 0.03125 mb` of RAM allocated on every request. Or 1mb every 32 requests.
To look at raw speed:
```ruby
require 'benchmark/ips'
number_of_objects_reduced = 1_114
Benchmark.ips do |x|
x.report("freeze") { number_of_objects_reduced.times { " ".freeze } }
x.report("no-freeze") { number_of_objects_reduced.times { " " } }
end
```
We get the results
```
Calculating -------------------------------------
freeze 1.428k i/100ms
no-freeze 609.000 i/100ms
-------------------------------------------------
freeze 14.363k (± 8.5%) i/s - 71.400k
no-freeze 6.084k (± 8.1%) i/s - 30.450k
```
Now we can do some maths:
```ruby
ips = 6_226k # iterations / 1 second
call_time_before = 1.0 / ips # seconds per iteration
ips = 15_254 # iterations / 1 second
call_time_after = 1.0 / ips # seconds per iteration
diff = call_time_before - call_time_after
number_of_objects_reduced * diff * 100
# => 0.4530373333993266 miliseconds saved per request
```
So we're shaving off 1 second of execution time for every 220 requests.
Is this going to be an insane speed boost to any Rails app: nope. Should we merge it: yep.
p.s. If you know of a method call that doesn't modify a string input such as [String#gsub](https://github.com/schneems/let_it_go/blob/b0e2da69f0cca87ab581022baa43291cdf48638c/lib/let_it_go/core_ext/string.rb#L37) please [give me a pull request to the appropriate file](https://github.com/schneems/let_it_go/blob/b0e2da69f0cca87ab581022baa43291cdf48638c/lib/let_it_go/core_ext/string.rb#L37), or open an issue in LetItGo so we can track and freeze more strings.
Keep those strings Frozen
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The type from the column is never used, except when being passed to the
attributes API. While leaving the type on the column wasn't necessarily
a bad thing, I worry that it's existence there implies that it is
something which should be used.
During the design and implementation process of the attributes API,
there have been plenty of cases where getting the "right" type object
was hard, but I had easy access to the column objects. For any
contributor who isn't intimately familiar with the intents behind the
type casting system, grabbing the type from the column might easily seem
like the "correct" thing to do.
As such, the goal of this change is to express that the column is not
something that should be used for type casting. The only places that are
"valid" (at the time of this commit) uses of acquiring a type object
from the column are fixtures (as the YAML file is going to mirror the
database more closely than the AR object), and looking up the type
during schema detection to pass to the attributes API
Many of the failing tests were removed, as they've been made obsolete
over the last year. All of the PG column tests were testing nothing
beyond polymorphism. The Mysql2 tests were duplicating the mysql tests,
since they now share a column class.
The implementation is a little hairy, and slightly verbose, but it felt
preferable to going back to 20 constructor options for the columns. If
you are git blaming to figure out wtf I was thinking with them, and have
a better idea, go for it. Just don't use a type object for this.
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