SERVER-61018 Create a generic histogram type

5 files changed, 357 insertions, 289 deletions

diff --git a/src/mongo/util/SConscript b/src/mongo/util/SConscript
index 3998716f7f4..e797a415281 100644
--- a/src/mongo/util/SConscript
+++ b/src/mongo/util/SConscript
@@ -695,7 +695,7 @@ icuEnv.CppUnitTest(
         'future_test_promise_void.cpp',
         'future_test_shared_future.cpp',
         'future_util_test.cpp',
-        'integer_histogram_test.cpp',
+        'histogram_test.cpp',
         'hierarchical_acquisition_test.cpp',
         'icu_test.cpp',
         'static_immortal_test.cpp',
diff --git a/src/mongo/util/histogram.h b/src/mongo/util/histogram.h
new file mode 100644
index 00000000000..0a07c82d9bc
--- /dev/null
+++ b/src/mongo/util/histogram.h
@@ -0,0 +1,187 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <algorithm>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/db/commands.h"
+#include "mongo/platform/atomic_word.h"
+#include "mongo/util/assert_util.h"
+
+namespace mongo {
+
+/**
+ * Generic histogram that supports data collection into intervals based on user-specified partitions
+ * over any continuous type. A binary predicate that establishes a strict weak ordering over the
+ * template parameter type `T` may be specified, otherwise `std::less<T>` is used. (read
+ * more here: https://en.cppreference.com/w/cpp/named_req/Compare).
+ *
+ * For some provided lowermost partition x and uppermost partition y, a value z will be counted
+ * in the (-inf, x) interval if z < x, and in the [y, inf) interval if z >= y. If no partitions are
+ * provided, z will be counted in the sole (-inf, inf) interval.
+ */
+template <typename T, typename Cmp = std::less<T>>
+class Histogram {
+    struct AtEnd {};
+
+public:
+    explicit Histogram(std::vector<T> partitions, Cmp comparator = {})
+        : _partitions{std::move(partitions)},
+          _counts(_partitions.size() + 1),
+          _comparator{std::move(comparator)} {
+
+        auto ordered =
+            std::adjacent_find(_partitions.begin(), _partitions.end(), [&](const T& a, const T& b) {
+                return !_comparator(a, b);
+            }) == _partitions.end();
+        if (!ordered) {
+            iasserted(6101800, "Partitions must be strictly monotonically increasing");
+        }
+    }
+
+    void increment(const T& data) {
+        auto i = std::upper_bound(_partitions.begin(), _partitions.end(), data, _comparator) -
+            _partitions.begin();
+
+        _counts[i].addAndFetch(1);
+    }
+
+    const std::vector<T>& getPartitions() const {
+        return _partitions;
+    }
+
+    std::vector<int64_t> getCounts() const {
+        std::vector<int64_t> r(_counts.size());
+        std::transform(
+            _counts.begin(), _counts.end(), r.begin(), [](auto&& x) { return x.load(); });
+        return r;
+    }
+
+    /**
+     * An input iterator over the Histogram class that provides access to histogram buckets, each
+     * containing the count, lower and upper bound values. The `lower` data member set to nullptr
+     * signifies the lowermost extremity of the distribution. nullptr similarly represents the
+     * uppermost extremity when assigned to the `upper` data member.
+     */
+    class iterator {
+    public:
+        struct Bucket {
+            int64_t count;
+            const T* lower;
+            const T* upper;
+        };
+
+        using difference_type = void;
+        using value_type = Bucket;
+        using pointer = const Bucket*;
+        using reference = const Bucket&;
+        using iterator_category = std::input_iterator_tag;
+
+        explicit iterator(const Histogram* hist) : _h{hist}, _pos{0} {}
+        iterator(const Histogram* hist, AtEnd) : _h{hist}, _pos{_h->_counts.size()} {}
+
+        reference operator*() const {
+            _b.count = _h->_counts[_pos].load();
+            _b.lower = (_pos == 0) ? nullptr : &_h->_partitions[_pos - 1];
+            _b.upper = (_pos == _h->_counts.size() - 1) ? nullptr : &_h->_partitions[_pos];
+            return _b;
+        }
+
+        pointer operator->() const {
+            return &**this;
+        }
+
+        iterator& operator++() {
+            ++_pos;
+            return *this;
+        }
+
+        iterator operator++(int) {
+            iterator orig = *this;
+            ++*this;
+            return orig;
+        }
+
+        friend bool operator==(const iterator& a, const iterator& b) {
+            return a._pos == b._pos;
+        }
+
+        friend bool operator!=(const iterator& a, const iterator& b) {
+            return !(a == b);
+        }
+
+    private:
+        const Histogram* _h;
+        size_t _pos;  // position into _h->_counts
+        mutable Bucket _b;
+    };
+
+    iterator begin() const {
+        return iterator(this);
+    }
+
+    iterator end() const {
+        return iterator(this, AtEnd{});
+    }
+
+private:
+    std::vector<T> _partitions;
+    std::vector<AtomicWord<int64_t>> _counts;
+    Cmp _comparator;
+};
+
+/**
+ * Appends data (i.e. count and lower/upper bounds of all buckets) of a histogram to the provided
+ * BSON object builder. `histKey` is used as the field name for the appended BSON object containing
+ * the data.
+ */
+template <typename T>
+void appendHistogram(BSONObjBuilder& bob, const Histogram<T>& hist, const StringData histKey) {
+    BSONObjBuilder histBob(bob.subobjStart(histKey));
+    long long totalCount = 0;
+
+    using namespace fmt::literals;
+    for (auto&& [count, lower, upper] : hist) {
+        std::string bucketKey = "{}{}, {})"_format(lower ? "[" : "(",
+                                                   lower ? "{}"_format(*lower) : "-inf",
+                                                   upper ? "{}"_format(*upper) : "inf");
+
+        BSONObjBuilder(histBob.subobjStart(bucketKey))
+            .append("count", static_cast<long long>(count));
+        totalCount += count;
+    }
+    histBob.append("totalCount", totalCount);
+}
+
+}  // namespace mongo
diff --git a/src/mongo/util/histogram_test.cpp b/src/mongo/util/histogram_test.cpp
new file mode 100644
index 00000000000..2e883335b6a
--- /dev/null
+++ b/src/mongo/util/histogram_test.cpp
@@ -0,0 +1,169 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/util/histogram.h"
+
+#include <boost/optional.hpp>
+
+#include "mongo/unittest/assert_that.h"
+#include "mongo/unittest/unittest.h"
+
+namespace mongo {
+
+namespace {
+
+using namespace unittest::match;
+using namespace std::literals;
+
+class HistogramTest : public unittest::Test {
+public:
+    template <typename T>
+    struct BucketSpec {
+        int64_t count;
+        boost::optional<T> lower, upper;
+
+        friend bool operator==(const BucketSpec& a, const BucketSpec& b) {
+            auto lens = [](auto&& x) { return std::tie(x.count, x.lower, x.upper); };
+            return lens(a) == lens(b);
+        }
+
+        friend std::ostream& operator<<(std::ostream& os, const BucketSpec& b) {
+            os << "count: " << b.count;
+            if (b.lower)
+                os << ", lower: " << *b.lower;
+            if (b.upper)
+                os << ", upper: " << *b.upper;
+            return os;
+        }
+    };
+
+    template <typename T>
+    boost::optional<T> ptrToOpt(const T* p) {
+        return p ? boost::optional<T>(*p) : boost::none;
+    }
+
+    template <typename T>
+    auto snapshot(const Histogram<T>& h) {
+        std::vector<BucketSpec<T>> r;
+        std::transform(h.begin(), h.end(), std::back_inserter(r), [&](auto&& b) {
+            return BucketSpec<T>{b.count, ptrToOpt(b.lower), ptrToOpt(b.upper)};
+        });
+        return r;
+    }
+};
+
+TEST_F(HistogramTest, CountsIncrementedAndStored) {
+    Histogram<int64_t> hist({0, 5, 8, 12});
+    for (int64_t i = 0; i < 15; ++i)
+        hist.increment(i);
+    std::vector<BucketSpec<int64_t>> expected = {
+        {0, {}, 0}, {5, 0, 5}, {3, 5, 8}, {4, 8, 12}, {3, 12, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+TEST_F(HistogramTest, CountsIncrementedInSmallestBucket) {
+    Histogram<int64_t> hist({5, 8, 12});
+    for (int64_t i = 0; i < 5; ++i)
+        hist.increment(i);
+    std::vector<BucketSpec<int64_t>> expected = {{5, {}, 5}, {0, 5, 8}, {0, 8, 12}, {0, 12, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+TEST_F(HistogramTest, CountsIncrementedAtPartition) {
+    std::vector<int64_t> origPartitions = {5, 8, 12};
+    Histogram<int64_t> hist(origPartitions);
+    for (auto& p : origPartitions)
+        hist.increment(p);
+    std::vector<BucketSpec<int64_t>> expected = {{0, {}, 5}, {1, 5, 8}, {1, 8, 12}, {1, 12, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+TEST_F(HistogramTest, NegativeValuesIncrementBuckets) {
+    Histogram<int64_t> hist({-12, -8, 5});
+    for (int64_t i = -15; i < 10; ++i)
+        hist.increment(i);
+    std::vector<BucketSpec<int64_t>> expected = {
+        {3, {}, -12}, {4, -12, -8}, {13, -8, 5}, {5, 5, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+TEST_F(HistogramTest, DurationCountsIncrementedAndStored) {
+    Histogram<Milliseconds> hist(
+        {Milliseconds{0}, Milliseconds{5}, Milliseconds{8}, Milliseconds{12}});
+    for (int64_t i = 0; i < 15; ++i)
+        hist.increment(Milliseconds{i});
+    std::vector<BucketSpec<Milliseconds>> expected = {{0, {}, Milliseconds{0}},
+                                                      {5, Milliseconds{0}, Milliseconds{5}},
+                                                      {3, Milliseconds{5}, Milliseconds{8}},
+                                                      {4, Milliseconds{8}, Milliseconds{12}},
+                                                      {3, Milliseconds{12}, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+TEST_F(HistogramTest, StringCountsIncrementedAndStoredByLength) {
+    Histogram<std::string> hist({"", "aa", "aaaaa", "aaaaaaaaa"});
+    for (int64_t i = 0; i < 12; ++i)
+        hist.increment(std::string(i, 'a'));
+    std::vector<BucketSpec<std::string>> expected = {{0, {}, ""s},
+                                                     {2, ""s, "aa"s},
+                                                     {3, "aa"s, "aaaaa"s},
+                                                     {4, "aaaaa"s, "aaaaaaaaa"s},
+                                                     {3, "aaaaaaaaa"s, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+TEST_F(HistogramTest, StringCountsIncrementedAndStoredByChar) {
+    Histogram<std::string> hist({"a", "h", "r", "z"});
+    for (char c = 'a'; c < 'a' + 25; ++c) {
+        hist.increment(std::string{c});
+    }
+    std::vector<BucketSpec<std::string>> expected = {
+        {0, {}, "a"s}, {7, "a"s, "h"s}, {10, "h"s, "r"s}, {8, "r"s, "z"s}, {0, "z"s, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+TEST_F(HistogramTest, SizeTCountsIncrementedAndStored) {
+    Histogram<size_t> hist({0, 5, 8, 12});
+    for (size_t i = 0; i < 15; ++i)
+        hist.increment(i);
+    std::vector<BucketSpec<size_t>> expected = {
+        {0, {}, 0}, {5, 0, 5}, {3, 5, 8}, {4, 8, 12}, {3, 12, {}}};
+
+    ASSERT_THAT(snapshot(hist), Eq(expected));
+}
+
+}  // namespace
+}  // namespace mongo
diff --git a/src/mongo/util/integer_histogram.h b/src/mongo/util/integer_histogram.h
deleted file mode 100644
index cab7447c26e..00000000000
--- a/src/mongo/util/integer_histogram.h
+++ /dev/null
@@ -1,119 +0,0 @@
-/**
- *    Copyright (C) 2021-present MongoDB, Inc.
- *
- *    This program is free software: you can redistribute it and/or modify
- *    it under the terms of the Server Side Public License, version 1,
- *    as published by MongoDB, Inc.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    Server Side Public License for more details.
- *
- *    You should have received a copy of the Server Side Public License
- *    along with this program. If not, see
- *    <http://www.mongodb.com/licensing/server-side-public-license>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the Server Side Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#pragma once
-
-#include "mongo/bson/bsonobjbuilder.h"
-#include "mongo/db/commands.h"
-#include <vector>
-
-namespace mongo {
-
-/**
- * Generalized version of OperationLatencyHistogram that can track latencies for any operation type
- * with custom lower bounds. For some provided lower bounds {x,y} a number z will be counted in the
- * x-y bucket if z ∈ [x, y). in the y-inf bucket if z ∈ [y, inf). and in the (-inf, x) bucket if z <
- * x.
- */
-template <std::size_t numLowerBounds>
-class IntegerHistogram {
-public:
-    const std::string kKey;
-
-    IntegerHistogram(std::string key, std::array<int64_t, numLowerBounds> lowerBounds)
-        : kKey(std::move(key)) {
-        invariant(!lowerBounds.empty(), "Lower bounds must not be empty");
-        _lowerBoundBuckets[0].lowerBound = std::numeric_limits<int64_t>::min();
-        int64_t prevVal = std::numeric_limits<int64_t>::min();
-        for (size_t i = 1; i < _lowerBoundBuckets.size(); ++i) {
-            auto lowerBoundVal = lowerBounds.at(i - 1);
-            invariant(lowerBoundVal > prevVal,
-                      "Lower bounds must be strictly monotonically increasing");
-
-            _lowerBoundBuckets[i].lowerBound = lowerBoundVal;
-            prevVal = lowerBoundVal;
-        }
-    }
-
-    void append(BSONObjBuilder& builder, bool shouldAppendAdditionalInfo) const {
-        BSONObjBuilder histogramBuilder(builder.subobjStart(kKey));
-        auto offsetToString = [this](size_t offset) {
-            if (offset == 0)
-                return std::string("-inf");
-            if (offset < _lowerBoundBuckets.size())
-                return std::to_string(_lowerBoundBuckets[offset].lowerBound);
-            return std::string("inf");
-        };
-
-        for (size_t i = 0; i < _lowerBoundBuckets.size(); i++) {
-            auto count = _lowerBoundBuckets[i].count.load();
-            if (count == 0)
-                continue;
-
-            auto key = fmt::format("{} - {}", offsetToString(i), offsetToString(i + 1));
-            BSONObjBuilder entryBuilder(histogramBuilder.subobjStart(key));
-            entryBuilder.append("count", (long long)(count));
-            entryBuilder.doneFast();
-        }
-
-        auto totalCount = _entryCount.load();
-        histogramBuilder.append("ops", (long long)totalCount);
-        if (shouldAppendAdditionalInfo && totalCount != 0) {
-            auto sum = _sum.load();
-            histogramBuilder.append("sum", (long long)sum);
-            histogramBuilder.append("mean", static_cast<double>(sum) / totalCount);
-        }
-        histogramBuilder.doneFast();
-    }
-
-    void increment(int64_t data) {
-        auto insertionIndex = std::upper_bound(_lowerBoundBuckets.begin(),
-                                               _lowerBoundBuckets.end(),
-                                               data,
-                                               [](const int64_t a, const LowerBoundBucket& b) {
-                                                   return a < b.lowerBound;
-                                               }) -
-            1;
-
-        insertionIndex->count.addAndFetch(1);
-        _entryCount.addAndFetch(1);
-        _sum.addAndFetch(data);
-    }
-
-private:
-    struct LowerBoundBucket {
-        int64_t lowerBound;
-        AtomicWord<int64_t> count;
-    };
-
-    std::array<LowerBoundBucket, numLowerBounds + 1> _lowerBoundBuckets;
-    AtomicWord<int64_t> _entryCount;
-    AtomicWord<int64_t> _sum;
-};
-}  // namespace mongo
diff --git a/src/mongo/util/integer_histogram_test.cpp b/src/mongo/util/integer_histogram_test.cpp
deleted file mode 100644
index 1a615cb5078..00000000000
--- a/src/mongo/util/integer_histogram_test.cpp
+++ /dev/null
@@ -1,169 +0,0 @@
-/**
- *    Copyright (C) 2021-present MongoDB, Inc.
- *
- *    This program is free software: you can redistribute it and/or modify
- *    it under the terms of the Server Side Public License, version 1,
- *    as published by MongoDB, Inc.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    Server Side Public License for more details.
- *
- *    You should have received a copy of the Server Side Public License
- *    along with this program. If not, see
- *    <http://www.mongodb.com/licensing/server-side-public-license>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the Server Side Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#include "mongo/platform/basic.h"
-#include "mongo/unittest/death_test.h"
-#include "mongo/unittest/unittest.h"
-#include "mongo/util/integer_histogram.h"
-
-namespace mongo {
-
-namespace {
-
-TEST(IntegerHistogram, EnsureCountsIncrementedAndStored) {
-    std::array<int64_t, 4> lowerBounds{0, 5, 8, 12};
-    IntegerHistogram<4> hist("testKey", lowerBounds);
-    int64_t sum = 0;
-    int64_t numInserts = 15;
-    for (int64_t i = 0; i < numInserts; i++) {
-        hist.increment(i);
-        sum += i;
-    }
-
-    auto out = [&] {
-        BSONObjBuilder builder;
-        hist.append(builder, true);
-        return builder.obj();
-    }();
-
-    auto buckets = out["testKey"];
-    ASSERT_EQUALS(buckets["0 - 5"]["count"].Long(), 5);
-    ASSERT_EQUALS(buckets["5 - 8"]["count"].Long(), 3);
-    ASSERT_EQUALS(buckets["8 - 12"]["count"].Long(), 4);
-    ASSERT_EQUALS(buckets["12 - inf"]["count"].Long(), 3);
-    ASSERT_EQUALS(buckets["ops"].Long(), numInserts);
-    ASSERT_EQUALS(buckets["sum"].Long(), sum);
-    ASSERT_EQUALS(buckets["mean"].Double(), static_cast<double>(sum) / numInserts);
-}
-
-TEST(IntegerHistogram, EnsureCountsIncrementedInSmallestBucket) {
-    std::array<int64_t, 3> lowerBounds{5, 8, 12};
-    IntegerHistogram<3> hist("testKey2", lowerBounds);
-    int64_t sum = 0;
-    int64_t numInserts = 5;
-    for (int64_t i = 0; i < numInserts; i++) {
-        hist.increment(i);
-        sum += i;
-    }
-
-    auto out = [&] {
-        BSONObjBuilder builder;
-        hist.append(builder, true);
-        return builder.obj();
-    }();
-
-    auto buckets = out["testKey2"];
-    ASSERT_EQUALS(buckets["-inf - 5"]["count"].Long(), 5);
-    ASSERT_EQUALS(buckets["ops"].Long(), numInserts);
-    ASSERT_EQUALS(buckets["sum"].Long(), sum);
-    ASSERT_EQUALS(buckets["mean"].Double(), static_cast<double>(sum) / numInserts);
-}
-
-TEST(IntegerHistogram, EnsureCountsCorrectlyIncrementedAtBoundary) {
-    std::array<int64_t, 3> lowerBounds{5, 8, 12};
-    IntegerHistogram<3> hist("testKey3", lowerBounds);
-    int64_t sum = 0;
-    int64_t numInserts = 3;
-    for (auto& boundary : lowerBounds) {
-        hist.increment(boundary);
-        sum += boundary;
-    }
-
-    auto out = [&] {
-        BSONObjBuilder builder;
-        hist.append(builder, true);
-        return builder.obj();
-    }();
-
-    auto buckets = out["testKey3"];
-    ASSERT_EQUALS(buckets["5 - 8"]["count"].Long(), 1);
-    ASSERT_EQUALS(buckets["8 - 12"]["count"].Long(), 1);
-    ASSERT_EQUALS(buckets["12 - inf"]["count"].Long(), 1);
-    ASSERT_EQUALS(buckets["ops"].Long(), numInserts);
-    ASSERT_EQUALS(buckets["sum"].Long(), sum);
-    ASSERT_EQUALS(buckets["mean"].Double(), static_cast<double>(sum) / numInserts);
-}
-
-TEST(IntegerHistogram, EnsureNegativeCountsIncrementBucketsCorrectly) {
-    std::array<int64_t, 3> lowerBounds{-12, -8, 5};
-    IntegerHistogram<3> hist("testKey4", lowerBounds);
-    int64_t sum = 0;
-    int64_t numInserts = 25;
-    for (int64_t i = -15; i < 10; i++) {
-        hist.increment(i);
-        sum += i;
-    }
-
-    auto out = [&] {
-        BSONObjBuilder builder;
-        hist.append(builder, true);
-        return builder.obj();
-    }();
-
-    auto buckets = out["testKey4"];
-    ASSERT_EQUALS(buckets["-inf - -12"]["count"].Long(), 3);
-    ASSERT_EQUALS(buckets["-12 - -8"]["count"].Long(), 4);
-    ASSERT_EQUALS(buckets["-8 - 5"]["count"].Long(), 13);
-    ASSERT_EQUALS(buckets["5 - inf"]["count"].Long(), 5);
-    ASSERT_EQUALS(buckets["ops"].Long(), numInserts);
-    ASSERT_EQUALS(buckets["sum"].Long(), sum);
-    ASSERT_EQUALS(buckets["mean"].Double(), static_cast<double>(sum) / numInserts);
-}
-
-TEST(IntegerHistogram, SkipsEmptyBuckets) {
-    std::array<int64_t, 2> lowerBounds{0, 5};
-    IntegerHistogram<2> hist("testKey6", lowerBounds);
-    hist.increment(6);
-
-    auto out = [&] {
-        BSONObjBuilder builder;
-        hist.append(builder, true);
-        return builder.obj();
-    }();
-
-    auto buckets = out["testKey6"];
-    ASSERT_THROWS(buckets["0 - 5"]["count"].Long(), DBException);
-    ASSERT_EQ(buckets["5 - inf"]["count"].Long(), 1);
-}
-
-DEATH_TEST(IntegerHistogram,
-           FailIfFirstLowerBoundIsMin,
-           "Lower bounds must be strictly monotonically increasing") {
-    std::array<int64_t, 2> lowerBounds{std::numeric_limits<int64_t>::min(), 5};
-    IntegerHistogram<2> hist("testKey5", lowerBounds);
-}
-
-DEATH_TEST(IntegerHistogram,
-           FailsWhenLowerBoundNotMonotonic,
-           "Lower bounds must be strictly monotonically increasing") {
-    std::array<int64_t, 2> lowerBounds{5, 0};
-    IntegerHistogram<2>("testKey7", lowerBounds);
-}
-}  // namespace
-}  // namespace mongo