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Differential D8499

rust-regex: increase the DFA size limit for the `regex` crate
ClosedPublic

Authored by Alphare on May 7 2020, 6:30 AM.

Details

Reviewers
None
Group Reviewers
hg-reviewers
Commits
rHGb15a37d85dbe: rust-regex: increase the DFA size limit for the `regex` crate
Summary

re2's DFA limit is already increased in rust/hg-core/src/re2/rust_re2.cpp,
the same has to be done for the regex crate.

Big repositories with big .hgignores will sometimes hit this limit and face
extreme performance regressions (I've seen one take *minutes* for hg status).

Diff Detail

Repository
rHG Mercurial
Lint
Automatic diff as part of commit; lint not applicable.
Unit
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

Alphare created this revision.May 7 2020, 6:30 AM
Alphare added a commit: rHGb15a37d85dbe: rust-regex: increase the DFA size limit for the `regex` crate.May 7 2020, 10:58 AM
This revision was not accepted when it landed; it landed in state Needs Review.
Closed by commit rHGb15a37d85dbe: rust-regex: increase the DFA size limit for the `regex` crate (authored by Alphare). · Explain Why
This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

PathPackages
Mrust/hg-core/src/matchers.rs (4 lines)

Diff 21279

rust/hg-core/src/matchers.rs

// Avoid the cost of UTF8 checking // Avoid the cost of UTF8 checking
// //
// # Safety // # Safety
// This is safe because we escaped all non-ASCII bytes. // This is safe because we escaped all non-ASCII bytes.
let pattern_string = unsafe { String::from_utf8_unchecked(escaped_bytes) }; let pattern_string = unsafe { String::from_utf8_unchecked(escaped_bytes) };
let re = regex::bytes::RegexBuilder::new(&pattern_string) let re = regex::bytes::RegexBuilder::new(&pattern_string)
.unicode(false) .unicode(false)
// Big repos with big `.hgignore` will hit the default limit and
// incur a significant performance hit. One repo's `hg status` hit
// multiple *minutes*.
.dfa_size_limit(50 * (1 << 20))
.build() .build()
.map_err(|e| PatternError::UnsupportedSyntax(e.to_string()))?; .map_err(|e| PatternError::UnsupportedSyntax(e.to_string()))?;
Ok(move |path: &HgPath| re.is_match(path.as_bytes())) Ok(move |path: &HgPath| re.is_match(path.as_bytes()))
} }
/// Returns the regex pattern and a function that matches an `HgPath` against /// Returns the regex pattern and a function that matches an `HgPath` against
/// said regex formed by the given ignore patterns. /// said regex formed by the given ignore patterns.