Abstract: This specification provides a database system, and primary database election methods and apparatuses. The system includes at least one auxiliary node and a plurality of clusters. If any cluster is a primary database of the first table and the other clusters are standby databases: the primary database applies to all auxiliary nodes and all clusters for extension of a term of the primary database during the current term, and if the primary database obtains more than half of approval votes before the current term ends, the primary database determines that the term of the primary database is successfully extended, otherwise, the primary database downgrades itself to a standby database; and the auxiliary node and/or the clusters that don't record the primary database of the first table in term initiate a distributed election, and elect a cluster that obtains more than half of approval votes as a new primary database.

Abstract: Embodiments of this specification provide a method and an apparatus for synchronously updating metadata in a distributed database. The distributed database includes a plurality of database nodes. A first node stores a first primary replica of a target replicated table, and a plurality of remaining second nodes store first backup replicas of the target replicated table. A full synchronization protocol is used between the first primary replica and the first backup replicas. The method is applied to the first node and includes: receiving an update request related to first metadata of a first data table in the distributed database; and writing update information related to the first metadata into the first primary replica based on the update request, to synchronize the update information to the respective first backup replicas of the plurality of second nodes based on the full synchronization protocol.

Abstract: Implementations of this specification provide methods and apparatuses for generating index entries. One method includes: acquiring a first sequence number of front large object data that is adjacent to a target data to be inserted in a large object data, wherein the first sequence number is generated based on a first code arrangement sequence and is comprised in a first index entry corresponding to the front large object data, in response to determining that the second sequence number immediately following the first sequence number is occupied, determining, based on a second code arrangement sequence, a branch index sequence number for the target data, and adding an index entry comprising the branch index sequence number to an index of the large object data, wherein the index entry is added between the first index entry comprising the first sequence number and a second index entry comprising the second sequence number.

Abstract: This application provides a method including updating a candidate state of the node based on a candidate state of an adjacent downstream node; updating a public identifier of the target node to a public identifier of the adjacent downstream node in response to that the candidate state of the adjacent downstream node is the first candidate state and the public identifier of the target node is less than the public identifier of the adjacent downstream node; and in response to that the candidate state of the adjacent downstream node is the first candidate state and a private identifier of the target node is equal to the public identifier of the adjacent downstream node, determining that a loop exists in a dependency path corresponding to the target node.

Abstract: A computer-implemented method for a database constraint relationship check, includes performing a data manipulation language (DML) operation of a first transaction for a target data table in the database. A submission stage is entered. A corresponding current transaction version number is determined for a target data record obtained and each latest related data record visible to the first transaction is read from the target data table or an associated data table of the target data table. A mutual limitation relationship exists between field values corresponding to a target field in the target data record and each related data record. A constraint relationship check is performed on a target field value corresponding to the target field in the target data record based on each related data record. The first transaction is submitted if the constraint relationship check succeeds or the first transaction is rolled back otherwise.

Abstract: This specification provides a database system, and primary database election methods and apparatuses. The system includes at least one auxiliary node and a plurality of clusters. If any cluster is a primary database of the first table and the other clusters are standby databases: the primary database applies to all auxiliary nodes and all clusters for extension of a term of the primary database during the current term, and if the primary database obtains more than half of approval votes before the current term ends, the primary database determines that the term of the primary database is successfully extended, otherwise, the primary database downgrades itself to a standby database; and the auxiliary node and/or the clusters that don't record the primary database of the first table in term initiate a distributed election, and elect a cluster that obtains more than half of approval votes as a new primary database.

Abstract: This specification discloses database service execution methods and apparatuses. An object deletion request can be received, and a to-be-deleted object can be determined. However, the to-be-deleted object is not immediately deleted, but an operation permission for the to-be-deleted object is modified, and a user is prohibited from accessing the to-be-deleted object. When an object restoration request that carries an object identifier is received, a to-be-deleted object corresponding to the object identifier is determined from each to-be-deleted object whose operation permission has been modified; and an operation permission for the to-be-deleted object corresponding to the object identifier is modified, and the user is allowed to access the to-be-deleted object corresponding to the object identifier.

Abstract: This specification discloses node election methods and apparatuses, storage media, and electronic devices. First, a target node device determines status information of all node devices when detecting that a master node device in a current term meets a predetermined resignation condition. Then, a candidate node device is determined from all the node devices based on the status information of all the node devices. Then, a voting request is broadcast to other node devices if it is determined that the candidate node device is the target node device. Broadcasting the voting request is skipped if it is determined that the candidate node device is another node device, and voting is performed for the another node device based on the determined candidate node device when a voting request that is broadcast by the another node device is received.

Abstract: Implementations of this specification provide methods and apparatuses for generating index entries. One method includes: acquiring a first sequence number of front large object data that is adjacent to a target data to be inserted in a large object data, wherein the first sequence number is generated based on a first code arrangement sequence and is comprised in a first index entry corresponding to the front large object data, in response to determining that the second sequence number immediately following the first sequence number is occupied, determining, based on a second code arrangement sequence, a branch index sequence number for the target data, and adding an index entry comprising the branch index sequence number to an index of the large object data, wherein the index entry is added between the first index entry comprising the first sequence number and a second index entry comprising the second sequence number.

Abstract: The present specification discloses a database disaster recovery system, method, and apparatus, a storage medium, and an electronic device. In the database disaster recovery system provided in the present specification, the system includes a first database. A data processing node in the first database synchronizes a log generated for a database operation to at least one data protection node based on a distributed consistency protocol. The data protection node receives and stores the log. In response to some data processing nodes in the first database experiencing an anomaly, a data processing node without an anomaly in the first database provides a database service based on logs stored in the data protection node, thereby implementing disaster recovery for the first database.

Abstract: Embodiments of this specification provide methods for configuring nodes in a distributed database, methods for synchronizing transaction logs in the distributed database, and the nodes in the distributed database. One method for configuring nodes includes: determining a first quantity of first nodes from N nodes in the distributed database, wherein the first nodes comprise a master node configured to synchronize transactions, the first quantity is an integer greater than N/2, and the first nodes determine a first transaction based on a distributed consistency protocol, and determining one or more of remaining nodes other than the first nodes in the N nodes as asynchronous nodes or election nodes, wherein the asynchronous nodes are configured to asynchronously receive the first transaction from the master node, and the election nodes are configured to modify at least the master node.

Abstract: A computer-implemented method for a database constraint relationship check, includes performing a data manipulation language (DML) operation of a first transaction for a target data table in the database. A submission stage is entered. A corresponding current transaction version number is determined for a target data record obtained and each latest related data record visible to the first transaction is read from the target data table or an associated data table of the target data table. A mutual limitation relationship exists between field values corresponding to a target field in the target data record and each related data record. A constraint relationship check is performed on a target field value corresponding to the target field in the target data record based on each related data record. The first transaction is submitted if the constraint relationship check succeeds or the first transaction is rolled back otherwise.

Abstract: This application provides a method including updating a candidate state of the node based on a candidate state of an adjacent downstream node; updating a public identifier of the target node to a public identifier of the adjacent downstream node in response to that the candidate state of the adjacent downstream node is the first candidate state and the public identifier of the target node is less than the public identifier of the adjacent downstream node; and in response to that the candidate state of the adjacent downstream node is the first candidate state and a private identifier of the target node is equal to the public identifier of the adjacent downstream node, determining that a loop exists in a dependency path corresponding to the target node.

Abstract: Embodiments of this specification provide a method and an apparatus for synchronously updating metadata in a distributed database. The distributed database includes a plurality of database nodes. A first node stores a first primary replica of a target replicated table, and a plurality of remaining second nodes store first backup replicas of the target replicated table. A full synchronization protocol is used between the first primary replica and the first backup replicas. The method is applied to the first node and includes: receiving an update request related to first metadata of a first data table in the distributed database; and writing update information related to the first metadata into the first primary replica based on the update request, to synchronize the update information to the respective first backup replicas of the plurality of second nodes based on the full synchronization protocol.

Abstract: The specification provides a method includes: updating a depth value of a target node or a depth value of a downstream node of the target node; receiving a depth value sent by an upstream node of the target node, and comparing the depth value of the target node with the depth value sent by the upstream node of the target node; in response to that the depth value of the target node is less than the depth value sent by the upstream node of the target node, updating the depth value of the target node to the depth value sent by the upstream node of the target node; and in response to that the depth value of the target node is equal to the depth value sent by the upstream node of the target node, determining that a loop exists in a data dependency path including the target node.

Abstract: Implementations of this specification provide methods and apparatuses for generating index entries. One method includes: acquiring a first sequence number of front large object data that is adjacent to a target data to be inserted in a large object data, wherein the first sequence number is generated based on a first code arrangement sequence and is comprised in a first index entry corresponding to the front large object data, in response to determining that the second sequence number immediately following the first sequence number is occupied, determining, based on a second code arrangement sequence, a branch index sequence number for the target data, and adding an index entry comprising the branch index sequence number to an index of the large object data, wherein the index entry is added between the first index entry comprising the first sequence number and a second index entry comprising the second sequence number.

Abstract: Implementations of this specification provide methods and apparatuses for generating index entries. One method includes: acquiring a first sequence number of front large object data that is adjacent to a target data to be inserted in a large object data, wherein the first sequence number is generated based on a first code arrangement sequence and is comprised in a first index entry corresponding to the front large object data, in response to determining that the second sequence number immediately following the first sequence number is occupied, determining, based on a second code arrangement sequence, a branch index sequence number for the target data, and adding an index entry comprising the branch index sequence number to an index of the large object data, wherein the index entry is added between the first index entry comprising the first sequence number and a second index entry comprising the second sequence number.

Abstract: An electrode structure of a flow battery. A density of the vertical tow in the electrode fiber is larger than the density of the parallel tow. In the electrode fiber per unit volume, the quantity ratio of the vertical tow to the parallel tow is at least 6:4. The electrode structure includes an odd number of layers of the electrode fibers, and the porosity of other layers is larger than that of the center layer. The electrode structure includes the vertical tows, so that, the contact area between the outer surface of the electrode and the adjacent component is increased and the contact resistance is reduced; the electrode has good mechanical properties; the contact resistance of such structure is reduced by 30%-50%; and the layers of the electrode have different thickness depending on the porosity. After compression, the layers with optimized thickness have a consistent porosity.

Abstract: The present specification describes an adaptive resource allocation method and apparatus. One example method includes determining a request time, an execution time, and a response time corresponding to a service statement executed by the database system during a time period, wherein the request time is a time at which the service statement was executed by the database system, the execution time is an amount of time allocated for execution of the service statement by the database system, and the response time is an amount of time that elapsed between the request time and a time at which execution of the service statement ended; identifying a time segment of the time period based on the request time; determining a service type associated with the service statement; and updating a resource quota for the time segment based on the service type, the execution time, and the response time for the service statement.

Abstract: The present specification describes an adaptive resource allocation method and apparatus. One example method includes determining a request time, an execution time, and a response time corresponding to a service statement executed by the database system during a time period, wherein the request time is a time at which the service statement was executed by the database system, the execution time is an amount of time allocated for execution of the service statement by the database system, and the response time is an amount of time that elapsed between the request time and a time at which execution of the service statement ended; identifying a time segment of the time period based on the request time; determining a service type associated with the service statement; and updating a resource quota for the time segment based on the service type, the execution time, and the response time for the service statement.