Feature #11158


Introduce a Symbol.count API as a more efficient alternative to Symbol.all_symbols.size

Added by methodmissing (Lourens Naudé) over 6 years ago. Updated over 6 years ago.

Target version:


We're in the process of migrating a very large Rails codebase from a Ruby 2.1.6 runtime to Ruby 2.2.2 and as part of this migration process would like to keep track of Symbol counts and Symbol GC efficiency in our metrics system. Preferably still while on 2.1 (however this implies a backport to 2.1 as well), but would definitely be useful in 2.2 as well.

Currently the recommended and only reliable way to get to the Symbol counts is via Symbol.all_symbols.size, which:

  • Allocates an Array
  • rb_ary_push and walking the symbol table isn't exactly efficient

Here's some benchmarks:

./miniruby -Ilib -rbenchmark -e "p Benchmark.measure { 10_000.times{ Symbol.count } }"
#<Benchmark::Tms:0x007f8bc208bdd0 @label="", @real=0.0011274919961579144, @cstime=0.0, @cutime=0.0, @stime=0.0, @utime=0.01, @total=0.01>
./miniruby -Ilib -rbenchmark -e "p Benchmark.measure { 10_000.times{ Symbol.all_symbols.size } }"
#<Benchmark::Tms:0x007fa47205a550 @label="", @real=0.3135859479953069, @cstime=0.0, @cutime=0.0, @stime=0.03, @utime=0.29, @total=0.31999999999999995>

I implemented and attached a patch for a simple Symbol.count API that just returns a numeric version of the symbol table size, without having to do any iteration.

Please let me know if this is inline with an expected core API, anything I could clean up further and if there's any possibility of such a change also being backported to 2.1 as well? (happy to create a new patch for 2.1)


symbol_count.patch (4.4 KB) symbol_count.patch Symbol.count patch file methodmissing (Lourens Naudé), 05/16/2015 04:12 AM
symbol_enumerator.patch (6.07 KB) symbol_enumerator.patch Symbol.each methodmissing (Lourens Naudé), 05/21/2015 02:14 AM

Related issues

Related to Ruby master - Feature #9963: Symbol.countFeedback06/19/2014Actions

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