Archive for February 15, 2018

• Ruby performance: Hash's #has_key? vs. #[] (square brackets)

  February 15, 2018

  During my time last year developing performance improvements for Rambling Trie, I stumbled into something quite interesting that happens with Ruby’s Hash class.

  A commonly used method from the Hash interface is #has_key? which tells you if the Hash in question contains a particular key. Rambling Trie’s underlying data structure is an n-ary tree backed by a Hash where each key is the letter corresponding to a child and each value is the Node that corresponds to that letter. As you might imagine, #has_key? is a common operation called throughout the gem implementation.

  To my surprise, while running some Ruby benchmarks I noticed that accessing the key with #[] and verifying if it was nil instead of calling #has_key? lowered the time it took…

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