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, 126 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/document_source_streaming_group.h b/src/mongo/db/pipeline/document_source_streaming_group.h
new file mode 100644
index 00000000000..bd72a3a7e7d
--- /dev/null
+++ b/src/mongo/db/pipeline/document_source_streaming_group.h
@@ -0,0 +1,126 @@
+/**
+ *    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 <memory>
+#include <utility>
+
+#include "mongo/db/pipeline/document_source_group_base.h"
+
+namespace mongo {
+
+/**
+ * This class represents streaming group implementation that can only be used when at least one of
+ * _id fields is monotonic. It stores and output groups in batches. All groups in the batch has
+ * the same value of monotonic id fields.
+ *
+ * For example, if the inputs are sorted by "x", we could use a batched streaming algorithm to
+ * perform the grouping for {$group: {_id: {x: "$x", y: "$y"}}}.
+ *
+ * Groups are processes in batches. One batch corresponds to a set of groups when each monotonic
+ * id field have the same value. Non-monotonic fields can have different values, so we still may
+ * have multiple groups and even spill to disk, but we still consume significanty less memory
+ * than general hash based group.
+ * When a document with a different value in at least one group id field is encountered, it is
+ * cached in '_firstDocumentOfNextBatch', current groups are finalized and returned in
+ * subsequent getNext() called and when the current batch is depleted, memory is freeed and the
+ * process starts again.
+ *
+ * TODO SERVER-71437 Implement an optimization for a special case where all group fields are
+ * monotonic
+ * - we don't need any hashing in this case.
+ */
+class DocumentSourceStreamingGroup final : public DocumentSourceGroupBase {
+public:
+    static constexpr StringData kStageName = "$_internalStreamingGroup"_sd;
+
+    const char* getSourceName() const final;
+
+    /**
+     * Convenience method for creating a new $_internalStreamingGroup stage. If maxMemoryUsageBytes
+     * is boost::none, then it will actually use the value of
+     * internalDocumentSourceGroupMaxMemoryBytes.
+     */
+    static boost::intrusive_ptr<DocumentSourceStreamingGroup> create(
+        const boost::intrusive_ptr<ExpressionContext>& expCtx,
+        const boost::intrusive_ptr<Expression>& groupByExpression,
+        std::vector<size_t> monotonicExpressionIndexes,
+        std::vector<AccumulationStatement> accumulationStatements,
+        boost::optional<size_t> maxMemoryUsageBytes = boost::none);
+
+    /**
+     * Parses 'elem' into a $_internalStreamingGroup stage, or throws a AssertionException if 'elem'
+     * was an invalid specification.
+     */
+    static boost::intrusive_ptr<DocumentSource> createFromBson(
+        BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);
+    static boost::intrusive_ptr<DocumentSource> createFromBsonWithMaxMemoryUsage(
+        BSONElement elem,
+        const boost::intrusive_ptr<ExpressionContext>& expCtx,
+        boost::optional<size_t> maxMemoryUsageBytes);
+
+protected:
+    GetNextResult doGetNext() final;
+
+    bool isSpecFieldReserved(StringData fieldName) final;
+    void serializeAdditionalFields(MutableDocument& out,
+                                   boost::optional<ExplainOptions::Verbosity> explain) const final;
+
+private:
+    static constexpr StringData kMonotonicIdFieldsSpecField = "$monotonicIdFields"_sd;
+
+    explicit DocumentSourceStreamingGroup(
+        const boost::intrusive_ptr<ExpressionContext>& expCtx,
+        boost::optional<size_t> maxMemoryUsageBytes = boost::none);
+
+
+    GetNextResult getNextDocument();
+
+    GetNextResult readyNextBatch();
+    /**
+     * Readies next batch after all children are initialized. See readyNextBatch() for
+     * more details.
+     */
+    GetNextResult readyNextBatchInner(GetNextResult input);
+
+    bool isBatchFinished(const Value& id);
+
+    template <typename IdValueGetter>
+    bool checkForBatchEndAndUpdateLastIdValues(const IdValueGetter& idValueGetter);
+
+    std::vector<size_t> _monotonicExpressionIndexes;
+    std::vector<Value> _lastMonotonicIdFieldValues;
+
+    boost::optional<Document> _firstDocumentOfNextBatch;
+
+    bool _sourceDepleted;
+};
+
+}  // namespace mongo