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rails--rails/activerecord/lib/active_record/explain.rb
yuuji.yaginuma 1b86d90136 Enable Performance/UnfreezeString cop
In Ruby 2.3 or later, `String#+@` is available and `+@` is faster than `dup`.

```ruby
# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  gem "benchmark-ips"
end

Benchmark.ips do |x|
  x.report('+@') { +"" }
  x.report('dup') { "".dup }
  x.compare!
end
```

```
$ ruby -v benchmark.rb
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
Warming up --------------------------------------
                  +@   282.289k i/100ms
                 dup   187.638k i/100ms
Calculating -------------------------------------
                  +@      6.775M (± 3.6%) i/s -     33.875M in   5.006253s
                 dup      3.320M (± 2.2%) i/s -     16.700M in   5.032125s

Comparison:
                  +@:  6775299.3 i/s
                 dup:  3320400.7 i/s - 2.04x  slower

```
2018-09-23 08:56:55 +09:00

50 lines
1.3 KiB
Ruby

# frozen_string_literal: true
require "active_record/explain_registry"
module ActiveRecord
module Explain
# Executes the block with the collect flag enabled. Queries are collected
# asynchronously by the subscriber and returned.
def collecting_queries_for_explain # :nodoc:
ExplainRegistry.collect = true
yield
ExplainRegistry.queries
ensure
ExplainRegistry.reset
end
# Makes the adapter execute EXPLAIN for the tuples of queries and bindings.
# Returns a formatted string ready to be logged.
def exec_explain(queries) # :nodoc:
str = queries.map do |sql, binds|
msg = +"EXPLAIN for: #{sql}"
unless binds.empty?
msg << " "
msg << binds.map { |attr| render_bind(attr) }.inspect
end
msg << "\n"
msg << connection.explain(sql, binds)
end.join("\n")
# Overriding inspect to be more human readable, especially in the console.
def str.inspect
self
end
str
end
private
def render_bind(attr)
value = if attr.type.binary? && attr.value
"<#{attr.value_for_database.to_s.bytesize} bytes of binary data>"
else
connection.type_cast(attr.value_for_database)
end
[attr.name, value]
end
end
end