Comments (4)
FWIW, here's a faster way to match two words in the same line: ^(?=.*?export)(?=.*?function)
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I don't mean to be pedantic, but I'll add a few comments since it's an interestic topic 🙂
The .NET regex engine supports timeouts (there's a constructor overload which takes a timeout parameter). This feature is mainly provided for searching with untrusted patterns in order to avoid DoS attacks. I haven't looked at how it's implemented but I believe a check is inserted when backtracking (and maybe in some other cases such as lookarounds). The check is simple enough but it still needs to retrieve the clock when enabled. In any case this article states:
Regex
supports timeouts, and guarantees that it will only do at mostO(n)
work (wheren
is the length of the input) between timeout checks
As for PCRE2, it has a PCRE2_AUTO_CALLOUT
flag which causes the engine to call a user-provided function before each pattern "item", and you can cancel execution from there, so in theory you could implement timeouts, but that would surely wreck the matching performance.
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^(?=.?export)(?=.?function)
It serves me well, thank you.
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Or also, rg export | rg function
.
Anyway, PCRE2 doesn't support a way to say, "if the search is taking longer than X time, stop." I don't know of any regex engine that supports that. If you think for a moment about how something like that would be implemented, it's pretty clear why: imagine trying to check a timeout value when you're in the middle of some vectorized SIMD loop. It would trash performance. And this sort of timeout check would need to be in virtually every loop everywhere. Ain't going to happen.
PCRE2, like most regex engines, does expose other types of resource limits. But none of them really approximate "time."
Your best bet is to filter out longer lines yourself (rg -v '.{100}'
or something), or use a technique that doesn't require using a backtracking engine. Hopefully some day #875 will happen and that will probably be the "right" way to solve your particular problem.
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Related Issues (20)
- The same `LineTerminator` is being used for searching and printing
- `--pre` doesn't work on Windows (CMD, MSYS2 bash, Powershell) HOT 16
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- Feature Request: search for binary data by supplying a hex string HOT 9
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- Allow following symlinks to files HOT 2
- WalkDir ignores files that are in .gitignore outside of current git repository HOT 2
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- BUG: exit code on windows not stable (wrong on first run, then stable), seems to leak HOT 9
- pcre2 reset match \K drops submatches HOT 1
- ripgrep is slower than LTREP matching `[A-Z][A-Z]+` HOT 3
- --files is listing files that won't be searched into HOT 4
- ripgrep ignore files inside `.github` folder HOT 5
- Potentially incorrect or undocumented .gitignore files handling
- `--text` flag only works if it's late in the command HOT 1
- Ripgrep parsing files in gitignore HOT 1
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- `--null-data` seems to inhibit some optimizations
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