Update upstream source from tag 'upstream/6.0.10'debian/6.0.10-1

Update to upstream version '6.0.10'
with Debian dir 2d176fa254eee97b139f712fec5709641335a8c3

1 files changed, 131 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/change_stream_split_event_helpers.cpp b/src/mongo/db/pipeline/change_stream_split_event_helpers.cpp
new file mode 100644
index 00000000000..19fba5afea5
--- /dev/null
+++ b/src/mongo/db/pipeline/change_stream_split_event_helpers.cpp
@@ -0,0 +1,131 @@
+/**
+ *    Copyright (C) 2023-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/change_stream_split_event_helpers.h"
+
+#include "mongo/db/pipeline/field_path.h"
+#include "mongo/db/pipeline/resume_token.h"
+
+namespace mongo {
+namespace change_stream_split_event {
+
+std::pair<Document, size_t> processChangeEventBeforeSplit(const Document& event,
+                                                          bool withMetadata) {
+    if (withMetadata) {
+        auto eventBson = event.toBsonWithMetaData<BSONObj::LargeSizeTrait>();
+        return {Document::fromBsonWithMetaData(eventBson), eventBson.objsize()};
+    } else {
+        // Serialize just the user data, and add the metadata fields separately.
+        auto eventBson = event.toBson<BSONObj::LargeSizeTrait>();
+        MutableDocument mutDoc(Document{eventBson});
+        mutDoc.copyMetaDataFrom(event);
+        return {mutDoc.freeze(), eventBson.objsize()};
+    }
+}
+
+std::queue<Document> splitChangeEvent(const Document& event,
+                                      size_t maxFragmentBsonSize,
+                                      size_t skipFirstFragments) {
+    // Extract the underlying BSON. We expect the event to be trivially convertible either with
+    // or without metadata, so we attempt to optimize the serialization here.
+    auto eventBson =
+        (event.isTriviallyConvertible() ? event.toBson<BSONObj::LargeSizeTrait>()
+                                        : event.toBsonWithMetaData<BSONObj::LargeSizeTrait>());
+
+    // Construct a sorted map of fields ordered by size and key for a deterministic greedy strategy
+    // to minimize the total number of fragments (the first fragment contains as many fields as
+    // possible). Don't include the original '_id' field, since each fragment will have its own.
+    std::map<std::pair<size_t, std::string>, Value> sortedFieldMap;
+    for (auto it = event.fieldIterator(); it.more();) {
+        auto&& [key, value] = it.next();
+        if (key != kIdField) {
+            sortedFieldMap.emplace(std::make_pair(eventBson[key].size(), key), value);
+        }
+    }
+
+    uassert(7182502,
+            "Cannot split an empty event or an event containing solely '_id' field",
+            !sortedFieldMap.empty());
+
+    auto resumeTokenData =
+        ResumeToken::parse(event.metadata().getSortKey().getDocument()).getData();
+
+    std::list<MutableDocument> fragments;
+    for (auto it = sortedFieldMap.cbegin(); it != sortedFieldMap.cend();) {
+        // Update the resume token with the index of the fragment we're about to add.
+        resumeTokenData.fragmentNum = fragments.size();
+
+        // Add a new fragment at the end of the fragments list.
+        auto& fragment = fragments.emplace_back();
+
+        // Add fields required by all fragments.
+        ResumeToken token(resumeTokenData);
+        fragment.metadata().setSortKey(Value(token.toDocument()), true);
+        fragment.addField(kIdField, fragment.metadata().getSortKey());
+        fragment.addField(kSplitEventField,
+                          Value(Document{{kFragmentNumberField, static_cast<int>(fragments.size())},
+                                         {kTotalFragmentsField, 0}}));
+
+        auto fragmentBsonSize = static_cast<size_t>(fragment.peek().toBsonWithMetaData().objsize());
+
+        // Fill the fragment with as many fields as we can until we run out or exceed max size.
+        // Always make sure we add at least one new field on each iteration.
+        do {
+            fragment.addField(it->first.second /* field name */, it->second /* field value */);
+            fragmentBsonSize += it->first.first /* field size */;
+        } while (++it != sortedFieldMap.cend() &&
+                 fragmentBsonSize + it->first.first /* field size */ <= maxFragmentBsonSize);
+
+        uassert(7182500,
+                str::stream() << "Splitting change event failed: fragment size " << fragmentBsonSize
+                              << " is greater than maximum allowed fragment size "
+                              << maxFragmentBsonSize,
+                fragmentBsonSize <= maxFragmentBsonSize);
+    }
+
+    // Iterate over the fragments to populate the 'kTotalFragmentsField' field and freeze the final
+    // events.
+    const auto totalFragments = Value(static_cast<int>(fragments.size()));
+    const auto totalFragmentsFieldPath =
+        FieldPath::getFullyQualifiedPath(kSplitEventField, kTotalFragmentsField);
+
+    std::queue<Document> outputFragments;
+    for (auto [it, i] = std::make_pair(fragments.begin(), 0ULL); it != fragments.end(); ++it, ++i) {
+        // Do not insert first 'skipFirstFragments' into the output.
+        if (i >= skipFirstFragments) {
+            it->setNestedField(totalFragmentsFieldPath, totalFragments);
+            outputFragments.push(it->freeze());
+        }
+    }
+
+    return outputFragments;
+}
+
+}  // namespace change_stream_split_event
+}  // namespace mongo