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/**
* Copyright (C) 2020-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/update/update_oplog_entry_serialization.h"
#include "mongo/db/update/document_diff_serialization.h"
#include "mongo/db/update/update_oplog_entry_version.h"
namespace mongo::update_oplog_entry {
BSONObj makeDeltaOplogEntry(const doc_diff::Diff& diff) {
BSONObjBuilder builder;
builder.append("$v", static_cast<int>(UpdateOplogEntryVersion::kDeltaV2));
builder.append(kDiffObjectFieldName, diff);
return builder.obj();
}
namespace {
BSONElement extractNewValueForFieldFromV1Entry(const BSONObj& oField, StringData fieldName) {
// Check the '$set' section.
auto setElt = oField["$set"];
if (setElt.ok()) {
// The $set field in a $v:1 entry should always be an object.
invariant(setElt.type() == BSONType::Object);
return setElt.embeddedObject()[fieldName];
}
// The field is either in the $unset section, or was not modified at all.
return BSONElement();
}
BSONElement extractNewValueForFieldFromV2Entry(const BSONObj& oField, StringData fieldName) {
auto diffField = oField[kDiffObjectFieldName];
// Every $v:2 oplog entry should have a 'diff' field that is an object.
invariant(diffField.type() == BSONType::Object);
doc_diff::DocumentDiffReader reader(diffField.embeddedObject());
boost::optional<BSONElement> nextMod;
while ((nextMod = reader.nextUpdate()) || (nextMod = reader.nextInsert())) {
if (nextMod->fieldNameStringData() == fieldName) {
return *nextMod;
}
}
// The field may appear in the "delete" section or not at all.
return BSONElement();
}
FieldRemovedStatus isFieldRemovedByV1Update(const BSONObj& oField, StringData fieldName) {
auto unsetElt = oField["$unset"];
if (unsetElt.ok()) {
invariant(unsetElt.type() == BSONType::Object);
if (unsetElt.embeddedObject()[fieldName].ok()) {
return FieldRemovedStatus::kFieldRemoved;
}
}
return FieldRemovedStatus::kFieldNotRemoved;
}
FieldRemovedStatus isFieldRemovedByV2Update(const BSONObj& oField, StringData fieldName) {
auto diffField = oField[kDiffObjectFieldName];
// Every $v:2 oplog entry should have a 'diff' field that is an object.
invariant(diffField.type() == BSONType::Object);
doc_diff::DocumentDiffReader reader(diffField.embeddedObject());
boost::optional<StringData> nextDelete;
while ((nextDelete = reader.nextDelete())) {
if (*nextDelete == fieldName) {
return FieldRemovedStatus::kFieldRemoved;
}
}
return FieldRemovedStatus::kFieldNotRemoved;
}
} // namespace
UpdateType extractUpdateType(const BSONObj& updateDocument) {
// Use the "$v" field to determine which type of update this is. Note $v:1 updates were allowed
// to omit the $v field so that case must be handled carefully.
auto vElt = updateDocument[kUpdateOplogEntryVersionFieldName];
if (!vElt.ok()) {
// We're dealing with a $v:1 entry if the first field name starts with a '$'. Otherwise
// it's a replacement update, which does not have a specific version name.
if (updateDocument.firstElementFieldNameStringData().startsWith("$")) {
return UpdateType::kV1Modifier;
}
// The version field is missing and the first field is not prefixed by "$". This means we
// have a replacement update.
return UpdateType::kReplacement;
} else if (vElt.numberInt() == static_cast<int>(UpdateOplogEntryVersion::kUpdateNodeV1)) {
return UpdateType::kV1Modifier;
} else if (vElt.numberInt() == static_cast<int>(UpdateOplogEntryVersion::kDeltaV2)) {
return UpdateType::kV2Delta;
}
// Unrecognized oplog entry version.
MONGO_UNREACHABLE;
}
BSONElement extractNewValueForField(const BSONObj& oField, StringData fieldName) {
invariant(fieldName.find('.') == std::string::npos, "field name cannot contain dots");
auto type = extractUpdateType(oField);
if (type == UpdateType::kV1Modifier) {
return extractNewValueForFieldFromV1Entry(oField, fieldName);
} else if (type == UpdateType::kV2Delta) {
return extractNewValueForFieldFromV2Entry(oField, fieldName);
} else if (type == UpdateType::kReplacement) {
return oField[fieldName];
}
// Clearly an unsupported format.
MONGO_UNREACHABLE;
}
FieldRemovedStatus isFieldRemovedByUpdate(const BSONObj& oField, StringData fieldName) {
invariant(fieldName.find('.') == std::string::npos, "field name cannot contain dots");
auto type = extractUpdateType(oField);
if (type == UpdateType::kV1Modifier) {
return isFieldRemovedByV1Update(oField, fieldName);
} else if (type == UpdateType::kV2Delta) {
return isFieldRemovedByV2Update(oField, fieldName);
} else if (type == UpdateType::kReplacement) {
// The field was definitely *not* removed if it's still in the post image. Otherwise,
// we cannot tell if it was removed without looking at the pre image.
return oField.hasField(fieldName) ? FieldRemovedStatus::kFieldNotRemoved
: FieldRemovedStatus::kUnknown;
}
MONGO_UNREACHABLE;
}
} // namespace mongo::update_oplog_entry
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