Issue #9143 has been updated by avit (Andrew Vit).


Note, this can be worked around by doing `csv.header_converters << proc{|h| h.freeze }` but I think there should be some built-in optimization for this.
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Feature #9143: Optimize CSV to share hash key objects between rows
https://bugs.ruby-lang.org/issues/9143#change-43092

Author: avit (Andrew Vit)
Status: Open
Priority: Normal
Assignee: 
Category: lib
Target version: 


Currently, when CSV headers are strings, then each row receives a copy of the strings for hash keys. This patch is an optimization to share the same frozen string keys between all rows.

Please verify: in the implementation of `Hash::[]`, are strings the only object that is dup'd, or should other types be frozen so they aren't copied for each row too?


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