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filter: Optimize double wildcard expansion 

This only allocates a single slice to expand the double wildcard and
only copies the pattern prefix once.

name                          old time/op    new time/op    delta
FilterPatterns/Relative-4       22.7ms ± 5%    23.3ms ± 9%     ~     (p=0.353 n=10+10)
FilterPatterns/Absolute-4       14.2ms ±13%    13.9ms ± 7%     ~     (p=0.853 n=10+10)
FilterPatterns/Wildcard-4        266ms ±16%      51ms ± 7%  -80.67%  (p=0.000 n=10+9)
FilterPatterns/ManyNoMatch-4     554ms ± 6%     551ms ± 9%     ~     (p=0.436 n=10+10)

name                          old alloc/op   new alloc/op   delta
FilterPatterns/Relative-4       3.57MB ± 0%    3.57MB ± 0%     ~     (p=0.349 n=10+10)
FilterPatterns/Absolute-4       3.57MB ± 0%    3.57MB ± 0%     ~     (p=0.073 n=10+9)
FilterPatterns/Wildcard-4        141MB ± 0%      14MB ± 0%  -89.89%  (p=0.000 n=10+9)
FilterPatterns/ManyNoMatch-4    3.57MB ± 0%    3.57MB ± 0%     ~     (all equal)

name                          old allocs/op  new allocs/op  delta
FilterPatterns/Relative-4        22.2k ± 0%     22.2k ± 0%     ~     (all equal)
FilterPatterns/Absolute-4        22.2k ± 0%     22.2k ± 0%     ~     (all equal)
FilterPatterns/Wildcard-4        1.63M ± 0%     0.09M ± 0%  -94.56%  (p=0.000 n=10+10)
FilterPatterns/ManyNoMatch-4     22.2k ± 0%     22.2k ± 0%     ~     (all equal)
This commit is contained in:
Michael Eischer 2020-10-07 15:51:17 +02:00
parent 7959796269
commit 17c53efb0d
1 changed files with 8 additions and 4 deletions
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12
internal/filter/filter.go
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@ -123,11 +123,15 @@ func hasDoubleWildcard(list Pattern) (ok bool, pos int) {
func match(patterns Pattern, strs []string) (matched bool, err error) {
if ok, pos := hasDoubleWildcard(patterns); ok {
// gradually expand '**' into separate wildcards
newPat := make(Pattern, len(strs))
// copy static prefix once
copy(newPat, patterns[:pos])
for i := 0; i <= len(strs)-len(patterns)+1; i++ {
newPat := make(Pattern, pos)
copy(newPat, patterns[:pos])
for k := 0; k < i; k++ {
newPat = append(newPat, "*")
// limit to static prefix and already appended '*'
newPat := newPat[:pos+i]
// in the first iteration the wildcard expands to nothing
if i > 0 {
newPat[pos+i-1] = "*"
}
newPat = append(newPat, patterns[pos+1:]...)