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regexp: support case-insensitive prefix strings #48955

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bboreham opened this issue Oct 13, 2021 · 2 comments
Open

regexp: support case-insensitive prefix strings #48955

bboreham opened this issue Oct 13, 2021 · 2 comments
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NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Performance
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@bboreham
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For a pattern like foo.*bar, the regexp compiler will extract the string "foo" and search for it using strings.Index before trying anything else.

I propose that this be extended to the case-insensitive version (?i)foo.*bar.

I did a trial implementation just calling strings.EqualFold repeatedly, and it is much faster:

name                old time/op    new time/op     delta
Match/Easy0i/16-8     2.99ns ± 1%     2.91ns ± 1%    -2.74%  (p=0.008 n=5+5)
Match/Easy0i/32-8      589ns ± 1%       56ns ± 0%   -90.51%  (p=0.008 n=5+5)
Match/Easy0i/1K-8     17.3µs ± 2%      7.5µs ± 5%   -56.52%  (p=0.008 n=5+5)
Match/Easy0i/32K-8     693µs ± 0%      259µs ± 0%   -62.61%  (p=0.008 n=5+5)
Match/Easy0i/1M-8     22.8ms ± 6%      8.4ms ± 1%   -63.28%  (p=0.008 n=5+5)
Match/Easy0i/32M-8     714ms ± 1%      269ms ± 0%   -62.32%  (p=0.008 n=5+5)

name                old speed      new speed       delta
Match/Easy0i/16-8   5.35GB/s ± 1%   5.50GB/s ± 1%    +2.82%  (p=0.008 n=5+5)
Match/Easy0i/32-8   54.3MB/s ± 1%  572.6MB/s ± 0%  +954.04%  (p=0.008 n=5+5)
Match/Easy0i/1K-8   59.1MB/s ± 2%  135.9MB/s ± 5%  +130.11%  (p=0.008 n=5+5)
Match/Easy0i/32K-8  47.3MB/s ± 0%  126.5MB/s ± 0%  +167.44%  (p=0.008 n=5+5)
Match/Easy0i/1M-8   46.0MB/s ± 6%  125.0MB/s ± 1%  +171.98%  (p=0.008 n=5+5)
Match/Easy0i/32M-8  47.0MB/s ± 1%  124.8MB/s ± 0%  +165.39%  (p=0.008 n=5+5)
@toothrot toothrot added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Oct 15, 2021
@toothrot toothrot added this to the Backlog milestone Oct 15, 2021
@seankhliao
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feel free to send a CL / PR with benchmarks

@gopherbot
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Change https://golang.org/cl/358756 mentions this issue: regexp: handle prefix string with fold-case

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