Abstract: Systems and methods are disclosed to implement, in a database system, database engine nodes that implement multi-page writes as an atomic operation. In embodiments, the database system may include multiple database engine nodes that optimistically perform page writes locally without checking for potential conflicts at a shared storage system. The storage system will detect and report conflicting writes on a single page. To ensure that a group of writes to multiple pages occur atomically, the database engine node maintains a transaction context for the group, so that if a page conflict is later detected for any write in the group, the entire group will be rolled back at the database engine node and the storage system. In embodiments, the transaction context will track subsequent writes generated by the node to any page written by the group, so that these subsequent writes are also rolled back with the group.

Abstract: Systems, methods, and computer-readable media are disclosed for an improved database. The systems, methods, and computer-readable media described herein may enhance the response time of databases and improve user experiences. In an example method described herein, a database may receive a search request for data stored in the database. The database may be stored in association with a b-tree to facilitate searching and retrieving data from the database. The method may include allocating a portion of a first memory for read ahead operations and performing the read ahead operations, wherein the read ahead operations comprise loading, into the portion of the first memory, data associated with one or more siblings of a current node, wherein the one or more siblings of the current node are one or more nodes that have a same number of parent nodes as the current node.

Abstract: Techniques for making machine learning inference calls for database query processing are described. In some embodiments, a method of making machine learning inference calls for database query processing may include generating a first batch of machine learning requests based at least on a query to be performed on data stored in a database service, wherein the query identifies a machine learning service, sending the first batch of machine learning requests to an input buffer of an asynchronous request handler, the asynchronous request handler to generate a second batch of machine learning requests based on the first batch of machine learning requests, and obtaining a plurality of machine learning responses from an output buffer of the asynchronous request handler, the machine learning responses generated by the machine learning service using a machine learning model in response to receiving the second batch of machine learning requests.

Abstract: A replica database may receive a replication instruction from a master. The replica may maintain a version of a collection of data in database pages stored on a storage device. A replication thread may process the instruction. The replication thread may determine that an item affected by the instruction is located in a page that is both loaded into a memory buffer and subject to contention. The page may be modified with information indicating that the instruction has not been processed. A subsequent reader thread may, while processing a request to access the page, apply the instruction and complete processing of the request.

Abstract: Online reordering for database table columns may allow a user to reorder the columns of a database table without taking the database offline. A mapping between different column orders for a database table may be generated and stored in response to a request to reorder columns in a database table. When a portion of the database table is accessed, the columns of the database table in the accessed portion of the database table may be reordered to perform the access request.

Abstract: A data store may implement on-demand data schema modifications. Request to change a schema for a data set in a data store may be received and a description of the change recorded as part of a schema history for the data set. The request to change the schema may then be acknowledged. When access requests directed to the data set are received at the data store, the schema history for the data set may be evaluated. If the schema history indicates that data that is to be accessed in order to service the data store needs to include one or more changes in the schema history, then a version of the schema that includes the one or more changes may be applied to the data.

Abstract: A database system may implement asynchronous processing for synchronous requests received at the database. A pool of request processing threads may be maintained. As access requests for the database are received from clients, an available request processing thread in the pool may process the access request. The access request may be dependent on a persistent storage I/O operation, such that processing of the access request waits at least until the persistent storage I/O operation is complete. The request processing thread may perform processing operations for the access request so that persistent storage I/O operation is performed and become available to process other access requests. A response processing thread may determine that the persistent storage I/O operation for the access request is complete, and send a response to the client.

Abstract: A lock-free data structure may be used to provide concurrent access to a data retention index for a data store. Different processes may obtain keys to the data retention index from the lock-free data structure. The different processes may update entries in the data retention index corresponding to the keys to identify data objects to retain in the data store. The data retention index may be evaluated to determine data objects not identified in the data retention index and reclaim portions of the data store that store the determined data objects for storing other data.

Abstract: Filtered generation of hash tables may be implemented as part of performing a hash join. A database query may be received that causes a hash join to be performed in order to join two database tables. A filtered generated from a scan of one of the tables that indicates which data in the table can satisfy a join predicate for the hash join may be applied to generate a hash table from a portion of the other table. The filtered hash table may then be used to evaluate whether portions of the tables can be joined in satisfaction of the join predicate for the hash join.

Abstract: A system for updating a database instance with a patch or new binary image. A database instance includes a database engine and a client-side storage layer driver to manage database state information and volume geometry state information associated with client process connections to a volume of a storage layer of a database system during the patching process. The database engine and the client-side storage service driver save database state information and volume geometry state information, execute the new binary image, and restore the updated database engine with the database state information and volume geometry state information. The new binary image may be executed using a fork/exec model, wherein file descriptors used to identify sockets used in existing client connections are preserved, enabling restoration of the client connections without interruption or downtime.

Abstract: Embodiments may include storing a query result in a results set cache with the query result being generated from execution of a particular query on a plurality of data records. One or more probabilistic data structures may be generated based, at least in part, on a subset of the data records that is reflected in the query result. An indication may be received that the plurality of data records has been modified. It may then be determined whether to invalidate the query result in the results set cache based, at least in part, on the one or more probabilistic data structures and a representation of modified plurality of data records.

Abstract: A stabilized optical pulse generator using RHML-FRL is provided. The stabilized optical pulse generator comprises an optical fiber ring composed of optical fibers, an optical amplifier and a modulator for optical modulation, an electric signal generator generating high frequency signals and an optical pulse stabilizer. The device generates an optical pulse train of repeating frequency of fm, when applying electric signals of frequency of fm to the modulator. Wherein, for a resonance frequency of the optical fibers of fc, the modulating frequency applying to the modulator is detuned from the electric signal of the frequency of fm by frequency of the resonance frequency fc divided by integer of p. Optical pulse trains of repeating frequency of p times of fm+fc/p or fm?fc/p are generated.

Abstract: The present invention relating to a device and method for multiplication of repetition frequency in optical pulse trains. The device and the method multiply repetition frequency of optical pulse train generated with ML-FRL with high stability. The device comprises an optical fiber ring composed of optical fibers, an optical amplifier and a modulator for optically modulating, and an electric signal generator generating high frequency signals. The device generates an optical pulse train of repeating frequency of fm, when applying electric signals of frequency of fm to the modulator. In addition to the construction, the stabilized optical pulse generator comprises a filter passing through frequencies of integer multiple of the applied modulation frequency fm, and a composite cavity composed of a plurality of optical fibers of which lengths are different each other.

Abstract: The present invention relating to a device and method for multiplication of repetition frequency in optical pulse trains. The device and the method multiply repetition frequency of optical pulse train generated with ML-FRL with high stability. The device comprises an optical fibre ring composed of optical fibres, an optical amplifier and a modulator for optically modulating, and an electric signal generator generating high frequency signals. The device generates an optical pulse train of repeating frequency of fm, when applying electric signals of frequency of fm to the modulator. In addition to the construction, the stabilised optical pulse generator comprises a filter passing through frequencies of integer multiple of the applied modulation frequency fm, and a composite cavity composed of a plurality of optical fibres of which lengths are different each other.

Abstract: A stabilized optical pulse generator using RHML-FRL is provided. The stabilized optical pulse generator comprises an optical fiber ring composed of optical fibers, an optical amplifier and a modulator for optical modulation, an electric signal generator generating high frequency signals and an optical pulse stabilizer. The device generates an optical pulse train of repeating frequency of fm, when applying electric signals of frequency of fm to the modulator. Wherein, for a resonance frequency of the optical fibers of fc, the modulating frequency applying to the modulator is detuned from the electric signal of the frequency of fm by frequency of the resonance frequency fc divided by integer of p. Optical pulse trains of repeating frequency of p times of fm+fc/p or fm−fc/p are generated.