C++ MutableDocument::setSortKeyMetaField方法代码示例

Document Document::fromBsonWithMetaData(const BSONObj& bson) {
    MutableDocument md;

    BSONObjIterator it(bson);
    while (it.more()) {
        BSONElement elem(it.next());
        auto fieldName = elem.fieldNameStringData();
        if (fieldName[0] == '$') {
            if (fieldName == metaFieldTextScore) {
                md.setTextScore(elem.Double());
                continue;
            } else if (fieldName == metaFieldRandVal) {
                md.setRandMetaField(elem.Double());
                continue;
            } else if (fieldName == metaFieldSortKey) {
                md.setSortKeyMetaField(elem.Obj());
                continue;
            }
        }

        // Note: this will not parse out metadata in embedded documents.
        md.addField(fieldName, Value(elem));
    }

    return md.freeze();
}

//.........这里部分代码省略.........
            }
            documentKey = input[repl::OplogEntry::kObject2FieldName];
            break;
        }
        case repl::OpTypeEnum::kCommand: {
            if (!input.getNestedField("o.drop").missing()) {
                operationType = DocumentSourceChangeStream::kDropCollectionOpType;

                // The "o.drop" field will contain the actual collection name.
                nss = NamespaceString(nss.db(), input.getNestedField("o.drop").getString());
            } else if (!input.getNestedField("o.renameCollection").missing()) {
                operationType = DocumentSourceChangeStream::kRenameCollectionOpType;

                // The "o.renameCollection" field contains the namespace of the original collection.
                nss = NamespaceString(input.getNestedField("o.renameCollection").getString());

                // The "o.to" field contains the target namespace for the rename.
                const auto renameTargetNss =
                    NamespaceString(input.getNestedField("o.to").getString());
                doc.addField(DocumentSourceChangeStream::kRenameTargetNssField,
                             Value(Document{{"db", renameTargetNss.db()},
                                            {"coll", renameTargetNss.coll()}}));
            } else if (!input.getNestedField("o.dropDatabase").missing()) {
                operationType = DocumentSourceChangeStream::kDropDatabaseOpType;

                // Extract the database name from the namespace field and leave the collection name
                // empty.
                nss = NamespaceString(nss.db());
            } else {
                // All other commands will invalidate the stream.
                operationType = DocumentSourceChangeStream::kInvalidateOpType;
            }

            // Make sure the result doesn't have a document key.
            documentKey = Value();
            break;
        }
        case repl::OpTypeEnum::kNoop: {
            operationType = DocumentSourceChangeStream::kNewShardDetectedOpType;
            // Generate a fake document Id for NewShardDetected operation so that we can resume
            // after this operation.
            documentKey = Value(Document{{DocumentSourceChangeStream::kIdField,
                                          input[repl::OplogEntry::kObject2FieldName]}});
            break;
        }
        default: { MONGO_UNREACHABLE; }
    }

    // UUID should always be present except for invalidate and dropDatabase entries.
    if (operationType != DocumentSourceChangeStream::kInvalidateOpType &&
        operationType != DocumentSourceChangeStream::kDropDatabaseOpType) {
        invariant(!uuid.missing(), "Saw a CRUD op without a UUID");
    }

    // Note that 'documentKey' and/or 'uuid' might be missing, in which case they will not appear
    // in the output.
    auto resumeTokenData = getResumeToken(ts, uuid, documentKey);
    auto resumeToken = ResumeToken(resumeTokenData).toDocument();

    // Add some additional fields only relevant to transactions.
    if (_txnContext) {
        doc.addField(DocumentSourceChangeStream::kTxnNumberField,
                     Value(static_cast<long long>(_txnContext->txnNumber)));
        doc.addField(DocumentSourceChangeStream::kLsidField, Value(_txnContext->lsid));
    }

    doc.addField(DocumentSourceChangeStream::kIdField, Value(resumeToken));
    doc.addField(DocumentSourceChangeStream::kOperationTypeField, Value(operationType));
    doc.addField(DocumentSourceChangeStream::kClusterTimeField, Value(resumeTokenData.clusterTime));

    // We set the resume token as the document's sort key in both the sharded and non-sharded cases,
    // since we will subsequently rely upon it to generate a correct postBatchResumeToken.
    // TODO SERVER-38539: when returning results for merging, we first check whether 'mergeByPBRT'
    // has been set. If not, then the request was sent from an older mongoS which cannot merge by
    // raw resume tokens, and we must use the old sort key format. This check, and the 'mergeByPBRT'
    // flag, are no longer necessary in 4.4; all change streams will be merged by resume token.
    if (pExpCtx->needsMerge && !pExpCtx->mergeByPBRT) {
        doc.setSortKeyMetaField(BSON("" << ts << "" << uuid << "" << documentKey));
    } else {
        doc.setSortKeyMetaField(resumeToken.toBson());
    }

    // "invalidate" and "newShardDetected" entries have fewer fields.
    if (operationType == DocumentSourceChangeStream::kInvalidateOpType ||
        operationType == DocumentSourceChangeStream::kNewShardDetectedOpType) {
        return doc.freeze();
    }

    doc.addField(DocumentSourceChangeStream::kFullDocumentField, fullDocument);
    doc.addField(DocumentSourceChangeStream::kNamespaceField,
                 operationType == DocumentSourceChangeStream::kDropDatabaseOpType
                     ? Value(Document{{"db", nss.db()}})
                     : Value(Document{{"db", nss.db()}, {"coll", nss.coll()}}));
    doc.addField(DocumentSourceChangeStream::kDocumentKeyField, documentKey);

    // Note that 'updateDescription' might be the 'missing' value, in which case it will not be
    // serialized.
    doc.addField("updateDescription", updateDescription);
    return doc.freeze();
}