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diff --git a/icing/join/document-id-to-join-info.h b/icing/join/document-id-to-join-info.h
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+++ b/icing/join/document-id-to-join-info.h
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+// Copyright (C) 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ICING_JOIN_DOCUMENT_ID_TO_JOIN_INFO_H_
+#define ICING_JOIN_DOCUMENT_ID_TO_JOIN_INFO_H_
+
+#include <utility>
+
+#include "icing/store/document-id.h"
+
+namespace icing {
+namespace lib {
+
+// DocumentIdToJoinInfo is composed of document_id and its join info.
+// - QualifiedId join: join info is the referenced document's namespace_id +
+//   fingerprint(uri).
+// - String join: join info is the term id.
+// - Integer join: join info is the integer.
+//
+// DocumentIdToJoinInfo will be stored in posting list.
+template <typename JoinInfoType>
+class DocumentIdToJoinInfo {
+ public:
+  static DocumentIdToJoinInfo<JoinInfoType> GetInvalid() {
+    return DocumentIdToJoinInfo<JoinInfoType>(kInvalidDocumentId,
+                                              JoinInfoType());
+  }
+
+  explicit DocumentIdToJoinInfo(DocumentId document_id, JoinInfoType join_info)
+      : document_id_(document_id), join_info_(std::move(join_info)) {}
+
+  DocumentId document_id() const { return document_id_; }
+  const JoinInfoType& join_info() const { return join_info_; }
+
+  bool is_valid() const { return IsDocumentIdValid(document_id_); }
+
+  bool operator<(const DocumentIdToJoinInfo<JoinInfoType>& other) const {
+    if (document_id_ != other.document_id_) {
+      return document_id_ < other.document_id_;
+    }
+    return join_info_ < other.join_info_;
+  }
+
+  bool operator==(const DocumentIdToJoinInfo<JoinInfoType>& other) const {
+    return document_id_ == other.document_id_ && join_info_ == other.join_info_;
+  }
+
+ private:
+  DocumentId document_id_;
+  JoinInfoType join_info_;
+} __attribute__((packed));
+
+}  // namespace lib
+}  // namespace icing
+
+#endif  // ICING_JOIN_DOCUMENT_ID_TO_JOIN_INFO_H_