Abstract: Implementations of this specification provide methods and apparatuses for replaying logs. One method includes: classifying a plurality of logs to be replayed into log queues, sending the log queues to a global replay queue, allocating one or more replay threads to the log queues based on rankings of the log queues in the global replay queue, wherein the one or more replay threads are configured to replay one or more current log queues of the log queues, and in response to identifying an error of a current log queue of the one or more current log queues in a replay process, allocating a replay thread of the one or more replay threads allocated to the current log queue to a log queue that immediately follows the current log queue in the global replay queue.

Abstract: Lease transfer between master and slave replicas is described. A master replicator determines that an initial master replica lease takes effect. On determining that a master replica transfer needs to be performed, sending a transfer preparation message to a target replicator prior to expiration of a current master replica lease. The target replicator locally starts and calculates a new master replica lease and returns a readiness response to the master replicator. The master replicator sends a lease extension message to remaining slave replicators to extend local corresponding leases. After receiving lease extension success responses of a majority of the slave replicators, the master replicator terminates the local master replica lease of the master replicator in advance, and sends a transfer confirmation message to the target replicator. The target replicator validates the new master replica lease to make the target replicator a new master replicator.

Abstract: This specification discloses example distributed table lock application methods and apparatuses, storage media, and electronic devices. In an example method, a master node receives a data processing request and determines a data table that to-be-processed data corresponding to the data processing request are located in. The master node generates a table lock for the data table; performs a lock operation on the data table and generates lock status information corresponding to the data table; writes the lock status information into a local log of the master node and synchronizes the log to a slave node such that the slave node stores the log. After the master node restarts, determines whether the master node stores the log; and in response to that the master node stores the log, restores the lock operation on the data table based on the lock status information recorded in the log.

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: Embodiments of this specification provide data filtering methods, computer-readable media and apparatuses for data queries. The filtering methods can be performed by a target device that serves as a storage node of a database. As an example, a target filtering operator involved in a query is determined. A target data block stored in the target device is obtained. Further, a pre-built operator function set is queried by using a data feature and an encoding feature of the target data block to obtain a target execution function of the target filtering operator. The operator function set is used to record filtering operator execution functions that are suitable for use and that correspond to various data types and various encoding manners. The target data block can be filtered by using the target execution function matched by the query to obtain a filtering result.

Abstract: Storage management by a target node for a distributed database includes sending, except the target node, a block query request to n?1 nodes of n nodes of a distributed jointly using a target memory storing some data blocks. N?1 to-be-reclaimed data block sets are received can combined with a to-be-reclaimed data block set maintained by the target node to obtain a combined data block set which is sent to the n?1 nodes. Each of the n?1 nodes removes a data block from the combined data block set and provides an obtained filtered data block set to the target node. The obtained filtered data block set and an n?1 filtered data block set sent by the n?1 nodes as n target data block sets is used by the target node. An overlapping data block of the n target data block sets is determined. The overlapping data block is reclaimed.

Abstract: Methods, systems, electronic devices and computer-readable media for database transaction processing are provided. In an example, after determining to perform primary-secondary switching of a copy, a first server records a context of a database transaction that is currently being executed, sends the context to a second server, and switches a primary copy stored in the first server to a secondary copy. The second server switches a secondary copy stored in the second server to a primary copy, and continues execution of the database transaction based on the context after completing the switching.

Abstract: Implementations of the present specification describe evicting a memory block in a cache, including determining a temperature index value of a memory block in a cache, where the memory block is a storage unit of the cache. Based on the temperature index value of the memory block in the cache, determining a to-be-evicted memory block that needs to be cleared in the cache. A target element in the to-be-evicted memory block is migrated to a target memory block in the cache, where the target memory block is a memory block that is retained in the cache and whose available storage space is greater than storage space required by the target element. The to-be-evicted memory block is deleted from the cache.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for accessing a relational database using requests that conform to a non-structure query language syntax. In one aspect, a method includes receiving, from a client, a first access request that conforms to a NoSQL syntax for accessing a wide column store, wherein the first access request comprises a first event feature and a first attribute feature that are related to the wide column store, and the first attribute feature comprises a column family feature of the wide column store; translating the first access request into a second access request that conforms to a SQL syntax, wherein the second access request comprises a second event feature corresponding to the first event feature and a second attribute feature corresponding to the first attribute feature; and forwarding the second access request to a relational database.

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: A data compression method includes: obtaining a to-be-compressed object; searching a recommendation record for a recommended compression coding rule that meets a compression rate condition, the recommendation record being configured to record a compression coding rule of a historical compressed object and corresponding compression rate information, and the historical compressed object being of a same type as the to-be-compressed object; and if the recommended compression coding rule that meets the compression rate condition is found, compressing the to-be-compressed object by using the recommended compression coding rule; and if the recommended compression coding rule that meets the compression rate condition is not found, starting a regular compression coding process to obtain estimated compression rates of a plurality of compression coding rules for the to-be-compressed object, selecting a target compression coding rule based on at least the estimated compression rates, and compressing the to-be-compressed

Abstract: Embodiments of the present specification provide a method for updating a database by using a two-phase commit distributed transaction. The method is applied to a coordinator, and includes: sending a first-phase prepare request message to each participant to end a current transaction, the current transaction being configured to update a target database record; and after receiving write lock advance release requests sent by all participants, returning a write lock advance release response to each participant to instruct each participant to unlock a target database record of the participant, the write lock advance release requests being sent by the participants after the participants successfully write a log of an update operation of the current transaction to a log buffer.

Abstract: Embodiments described herein provide a system for facilitating efficient indexing in a database. The system can maintain a data table in the database. The data table includes a first column for structured data and a second column for unstructured text. A row of the data table can include a first piece of data in the first column and a second piece of data in the second column. During operation, the system performs word segmentation on the second piece of data to generate a first set of semantically meaningful word segments. The system then generates a set of index entries that corresponds to the row. A respective index entry includes an index generated from the first piece of data and a corresponding word segment of the first set of semantically meaningful word segments.

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: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for accessing a relational database using requests that conform to a non-structure query language syntax. In one aspect, a method includes receiving, from a client, a first access request that conforms to a NoSQL syntax for accessing a wide column store, wherein the first access request comprises a first event feature and a first attribute feature that are related to the wide column store, and the first attribute feature comprises a column family feature of the wide column store; translating the first access request into a second access request that conforms to a SQL syntax, wherein the second access request comprises a second event feature corresponding to the first event feature and a second attribute feature corresponding to the first attribute feature; and forwarding the second access request to a relational database.

Abstract: The present specification discloses a database migration method, including: copying metadata from a first server of a database, the metadata including identification information of synthetic data; receiving a service instruction sent by a client after the copying the metadata from the first server of the database; determining, based on the service instruction, whether the synthetic data needs to be retrieved from the first server of the database; and in response to it is determined that the synthetic data needs to be retrieved from the first server of the database, copying the synthetic data from the first server of the database based on the identification information of the synthetic data. According to the present disclosure, the service instruction sent by the client is received in advance, and the synthetic data is copied from the first server of the database based on the identification information of the synthetic data, thereby reducing time taken for database migration.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for writing data in one or more storage units. One of the methods includes obtaining an erasing count for each of multiple storage units, wherein the erasing count equals a total count of erasing operations that have been performed on all blocks of the storage unit. The method further includes identifying one or more of the storage units that satisfy one or more conditions associated with writing data, determining a storage unit that has the smallest erasing count among the identified storage units, and writing the data in the determined storage unit.

Abstract: Implementations of the present application provide a partition splitting method. Data files in a target source partition are divided into at least two data groups. A first data group from the at least two data groups is selected as a target splitting data group. A first splitting step is performed on the target splitting data group, including: splitting the target splitting data group into a plurality of data sub-groups based on a predetermined splitting rule, wherein each data sub-group of the plurality of data sub-groups corresponds to a new partition of at least two new partitions for the target source partition, and assigning each data sub-group to the new partition corresponding to the data sub-group. A second data group from the at least two data groups is selected as the target splitting data group, wherein the second data group is different from the first data group.

Abstract: A database query optimization computer-implemented method, medium, and system are disclosed. In one computer-implemented method, a data query request sent by a client device is received and parsed. An execution plan for executing the data query request is determined based on a parsing result. If the execution plan is a nested loop anti-join, whether there is a possibility that a to-be-queried field in a to-be-queried data table indicated by the data query request contains a NULL value is determined. If there is a possibility that the to-be-queried field contains a NULL value, a filter condition is generated and the execution plan is optimized based on the filter condition.

Abstract: One or more implementations of the present specification disclose a database analysis information generation method, including: reading data in a to-be-merged data level and data in a merging data level; generating a new merging data level by merging the data in the to-be-merged data level and the data in the merging data level in a merging process; and performing an operation of generating new database analysis information based on data in the new merging data level and data in existing database analysis information in the process of generating the new merging data level.