Bug #18032: Openstruct is ~20..25x slower with Ruby 3.0.0 and 3.0.1 compared to earlier versions

• Status: Rejected
• Assignee: marcandre (Marc-Andre Lafortune)
• Target version: -
• ruby -v: 3.0.0
• Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN

[TiloS (Tilo S)]

Doing some timings with different Ruby versions, I noticed that when using Ruby 3.0.0 and 3.0.1
the time to create OpenStruct instances has significantly increased by 20..25x

0.936016 seconds elapsed for Class.new (Ruby 2.7.2)
0.453067 seconds elapsed for Struct (Ruby 2.7.2)
1.016676 seconds elapsed for Hash (Ruby 2.7.2)
1.482318 seconds elapsed for OpenStruct (Ruby 2.7.2)

0.421272 seconds elapsed for Class.new (Ruby 3.0.0)
0.322617 seconds elapsed for Struct (Ruby 3.0.0)
0.719928 seconds elapsed for Hash (Ruby 3.0.0)
35.130777 seconds elapsed for OpenStruct (Ruby 3.0.0) (oops!)

see also: https://stackoverflow.com/questions/1177594/when-should-i-use-struct-vs-openstruct/5440064#5440064

Can someone please look into this?

[mame (Yusuke Endoh)]

• Related to Bug #12136: OpenStruct.new(format: :bar).send :format # => too few arguments added

[mame (Yusuke Endoh)]

• Related to Bug #15409: OpenStruct error when attribute is called 'method' added

[mame (Yusuke Endoh)]

• Status changed from Open to Assigned
• Assignee set to marcandre (Marc-Andre Lafortune)

Maybe due to this change: https://bugs.ruby-lang.org/issues/15409#note-9

reverts lazy initialization and restores overriding private methods

I'm assigning this ticket to @marcandre (Marc-Andre Lafortune).

BTW, OpenStruct is now considered as "an antipattern", so I recommend you no longer to use OpenStruct.

[marcandre (Marc-Andre Lafortune)]

• Status changed from Assigned to Rejected

@mame (Yusuke Endoh) is correct that #15409 was a concern, but this is mainly due to #12136 and listed in the release notes for 3.0.

Basically we have prioritized correctness over performance and came back to a solution similar to that of Ruby 2.2.

Note that only initialization from a Hash was impacted, but setting the attributes one by one was not much impacted.

If the benchmarking code is changed:

# before
OpenStruct.new(:name => "User", :age => 21)
# after
o = OpenStruct.new
o.name = "User"
o.age = 21

You'll see that this similar code was always slow.

The documentation now states the multiple caveats of OpenStruct, one of which is performance.

A different class that would not define methods but use only method_missing would be faster, but not quite as accurate.

[TiloS (Tilo S)]

@mame (Yusuke Endoh) @marcandre (Marc-Andre Lafortune) that is unfortunate, because initializing from a hash is probably the most frequently used form.

I agree on correctness over perfomance - I ran into the issue with pre-defined methods before :)

Thank you for taking a look!