diff --git a/model/labels/labels_string.go b/model/labels/labels_string.go index e232ca7a4d..223aa6ebf7 100644 --- a/model/labels/labels_string.go +++ b/model/labels/labels_string.go @@ -273,13 +273,27 @@ func (ls Labels) Copy() Labels { // Get returns the value for the label with the given name. // Returns an empty string if the label doesn't exist. func (ls Labels) Get(name string) string { + if name == "" { // Avoid crash in loop if someone asks for "". + return "" // Prometheus does not store blank label names. + } for i := 0; i < len(ls.data); { - var lName, lValue string - lName, i = decodeString(ls.data, i) - lValue, i = decodeString(ls.data, i) - if lName == name { - return lValue + var size int + size, i = decodeSize(ls.data, i) + if ls.data[i] == name[0] { + lName := ls.data[i : i+size] + i += size + if lName == name { + lValue, _ := decodeString(ls.data, i) + return lValue + } + } else { + if ls.data[i] > name[0] { // Stop looking if we've gone past. + break + } + i += size } + size, i = decodeSize(ls.data, i) + i += size } return "" } @@ -422,37 +436,49 @@ func FromStrings(ss ...string) Labels { // Compare compares the two label sets. // The result will be 0 if a==b, <0 if a < b, and >0 if a > b. -// TODO: replace with Less function - Compare is never needed. -// TODO: just compare the underlying strings when we don't need alphanumeric sorting. func Compare(a, b Labels) int { - l := len(a.data) - if len(b.data) < l { - l = len(b.data) + // Find the first byte in the string where a and b differ. + shorter, longer := a.data, b.data + if len(b.data) < len(a.data) { + shorter, longer = b.data, a.data + } + i := 0 + // First, go 8 bytes at a time. Data strings are expected to be 8-byte aligned. + sp := unsafe.Pointer((*reflect.StringHeader)(unsafe.Pointer(&shorter)).Data) + lp := unsafe.Pointer((*reflect.StringHeader)(unsafe.Pointer(&longer)).Data) + for ; i < len(shorter)-8; i += 8 { + if *(*uint64)(unsafe.Add(sp, i)) != *(*uint64)(unsafe.Add(lp, i)) { + break + } + } + // Now go 1 byte at a time. + for ; i < len(shorter); i++ { + if shorter[i] != longer[i] { + break + } + } + if i == len(shorter) { + // One Labels was a prefix of the other; the set with fewer labels compares lower. + return len(a.data) - len(b.data) } - ia, ib := 0, 0 - for ia < l { - var aName, bName string - aName, ia = decodeString(a.data, ia) - bName, ib = decodeString(b.data, ib) - if aName != bName { - if aName < bName { - return -1 - } - return 1 - } - var aValue, bValue string - aValue, ia = decodeString(a.data, ia) - bValue, ib = decodeString(b.data, ib) - if aValue != bValue { - if aValue < bValue { - return -1 - } - return 1 + // Now we know that there is some difference before the end of a and b. + // Go back through the fields and find which field that difference is in. + firstCharDifferent := i + for i = 0; ; { + size, nextI := decodeSize(a.data, i) + if nextI+size > firstCharDifferent { + break } + i = nextI + size } - // If all labels so far were in common, the set with fewer labels comes first. - return len(a.data) - len(b.data) + // Difference is inside this entry. + aStr, _ := decodeString(a.data, i) + bStr, _ := decodeString(b.data, i) + if aStr < bStr { + return -1 + } + return +1 } // Copy labels from b on top of whatever was in ls previously, reusing memory or expanding if needed. diff --git a/model/labels/labels_test.go b/model/labels/labels_test.go index 108d8b0de0..d91be27cbc 100644 --- a/model/labels/labels_test.go +++ b/model/labels/labels_test.go @@ -361,6 +361,18 @@ func TestLabels_Compare(t *testing.T) { "bbc", "222"), expected: -1, }, + { + compared: FromStrings( + "aaa", "111", + "bb", "222"), + expected: 1, + }, + { + compared: FromStrings( + "aaa", "111", + "bbbb", "222"), + expected: -1, + }, { compared: FromStrings( "aaa", "111"), @@ -380,6 +392,10 @@ func TestLabels_Compare(t *testing.T) { "bbb", "222"), expected: 0, }, + { + compared: EmptyLabels(), + expected: 1, + }, } sign := func(a int) int { @@ -395,6 +411,8 @@ func TestLabels_Compare(t *testing.T) { for i, test := range tests { got := Compare(labels, test.compared) require.Equal(t, sign(test.expected), sign(got), "unexpected comparison result for test case %d", i) + got = Compare(test.compared, labels) + require.Equal(t, -sign(test.expected), sign(got), "unexpected comparison result for reverse test case %d", i) } } @@ -425,7 +443,8 @@ func TestLabels_Has(t *testing.T) { func TestLabels_Get(t *testing.T) { require.Equal(t, "", FromStrings("aaa", "111", "bbb", "222").Get("foo")) - require.Equal(t, "111", FromStrings("aaa", "111", "bbb", "222").Get("aaa")) + require.Equal(t, "111", FromStrings("aaaa", "111", "bbb", "222").Get("aaaa")) + require.Equal(t, "222", FromStrings("aaaa", "111", "bbb", "222").Get("bbb")) } // BenchmarkLabels_Get was written to check whether a binary search can improve the performance vs the linear search implementation @@ -445,7 +464,7 @@ func BenchmarkLabels_Get(b *testing.B) { maxLabels := 30 allLabels := make([]Label, maxLabels) for i := 0; i < maxLabels; i++ { - allLabels[i] = Label{Name: strings.Repeat(string('a'+byte(i)), 5)} + allLabels[i] = Label{Name: strings.Repeat(string('a'+byte(i)), 5+(i%5))} } for _, size := range []int{5, 10, maxLabels} { b.Run(fmt.Sprintf("with %d labels", size), func(b *testing.B) { @@ -456,6 +475,7 @@ func BenchmarkLabels_Get(b *testing.B) { {"get first label", allLabels[0].Name}, {"get middle label", allLabels[size/2].Name}, {"get last label", allLabels[size-1].Name}, + {"get not-found label", "benchmark"}, } { b.Run(scenario.desc, func(b *testing.B) { b.ResetTimer() @@ -468,27 +488,34 @@ func BenchmarkLabels_Get(b *testing.B) { } } +var comparisonBenchmarkScenarios = []struct { + desc string + base, other Labels +}{ + { + "equal", + FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), + FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), + }, + { + "not equal", + FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), + FromStrings("a_label_name", "a_label_value", "another_label_name", "a_different_label_value"), + }, + { + "different sizes", + FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), + FromStrings("a_label_name", "a_label_value"), + }, + { + "lots", + FromStrings("aaa", "bbb", "ccc", "ddd", "eee", "fff", "ggg", "hhh", "iii", "jjj", "kkk", "lll", "mmm", "nnn", "ooo", "ppp", "qqq", "rrz"), + FromStrings("aaa", "bbb", "ccc", "ddd", "eee", "fff", "ggg", "hhh", "iii", "jjj", "kkk", "lll", "mmm", "nnn", "ooo", "ppp", "qqq", "rrr"), + }, +} + func BenchmarkLabels_Equals(b *testing.B) { - for _, scenario := range []struct { - desc string - base, other Labels - }{ - { - "equal", - FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), - FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), - }, - { - "not equal", - FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), - FromStrings("a_label_name", "a_label_value", "another_label_name", "a_different_label_value"), - }, - { - "different sizes", - FromStrings("a_label_name", "a_label_value", "another_label_name", "another_label_value"), - FromStrings("a_label_name", "a_label_value"), - }, - } { + for _, scenario := range comparisonBenchmarkScenarios { b.Run(scenario.desc, func(b *testing.B) { b.ResetTimer() for i := 0; i < b.N; i++ { @@ -498,6 +525,17 @@ func BenchmarkLabels_Equals(b *testing.B) { } } +func BenchmarkLabels_Compare(b *testing.B) { + for _, scenario := range comparisonBenchmarkScenarios { + b.Run(scenario.desc, func(b *testing.B) { + b.ResetTimer() + for i := 0; i < b.N; i++ { + _ = Compare(scenario.base, scenario.other) + } + }) + } +} + func TestLabels_Copy(t *testing.T) { require.Equal(t, FromStrings("aaa", "111", "bbb", "222"), FromStrings("aaa", "111", "bbb", "222").Copy()) }