SERVER-55786 Update PartitionIterator memory usage when documents are released

This commit also handles the inflation of Documents as expressions are
evaluated due to the internal caching in the Document class.

1 files changed, 123 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/memory_usage_tracker_test.cpp b/src/mongo/db/pipeline/memory_usage_tracker_test.cpp
new file mode 100644
index 00000000000..f0514d86758
--- /dev/null
+++ b/src/mongo/db/pipeline/memory_usage_tracker_test.cpp
@@ -0,0 +1,123 @@
+/**
+ *    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/db/pipeline/memory_usage_tracker.h"
+#include "mongo/unittest/death_test.h"
+#include "mongo/unittest/unittest.h"
+
+namespace mongo {
+namespace {
+
+class MemoryUsageTrackerTest : public unittest::Test {
+public:
+    static constexpr auto kDefaultMax = 1 * 1024;  // 1KB max.
+    MemoryUsageTrackerTest()
+        : _tracker(false /** allowDiskUse */, kDefaultMax), _funcTracker(&_tracker) {}
+
+
+    MemoryUsageTracker _tracker;
+    MemoryUsageTracker::PerFunctionMemoryTracker _funcTracker;
+};
+
+TEST_F(MemoryUsageTrackerTest, SetUpdatesCurrentAndMax) {
+    _tracker.set(50LL);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 50LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 50LL);
+
+    _tracker.set(_tracker.currentMemoryBytes() + 50);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 100LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 100LL);
+}
+
+TEST_F(MemoryUsageTrackerTest, SetFunctionUsageUpdatesGlobal) {
+    _tracker.set(50LL);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 50LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 50LL);
+
+    // 50 global + 50 _funcTracker.
+    _funcTracker.set(50);
+    ASSERT_EQ(_funcTracker.currentMemoryBytes(), 50LL);
+    ASSERT_EQ(_funcTracker.maxMemoryBytes(), 50LL);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 100LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 100LL);
+
+    // New tracker adds another 50, 150 total.
+    _tracker.set("newTracker", 50);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 150LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 150LL);
+
+    // Lower usage of function tracker is reflected in global.
+    _tracker.set("newTracker", 0);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 100LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 150LL);
+}
+
+TEST_F(MemoryUsageTrackerTest, UpdateUsageUpdatesGlobal) {
+    _tracker.set(50LL);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 50LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 50LL);
+
+    // Add another 50 to the global, 100 total.
+    _tracker.update(50);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 100LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 100LL);
+
+    // Function tracker adds another 50, 150 total.
+    _funcTracker.update(50);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 150LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 150LL);
+
+    // Lower usage of function tracker is reflected in global.
+    _funcTracker.update(-25);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 125LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 150LL);
+}
+
+DEATH_TEST_F(MemoryUsageTrackerTest,
+             UpdateGlobalToNegativeIsDisallowed,
+             "Underflow on memory tracking") {
+    _tracker.set(50LL);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 50LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 50LL);
+
+    _tracker.update(-100);
+}
+
+DEATH_TEST_F(MemoryUsageTrackerTest,
+             UpdateFunctionUsageToNegativeIsDisallowed,
+             "Underflow on memory tracking") {
+    _funcTracker.set(50LL);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 50LL);
+    ASSERT_EQ(_tracker.maxMemoryBytes(), 50LL);
+
+    _funcTracker.update(-100);
+}
+
+}  // namespace
+}  // namespace mongo