Abstract: Methods, systems, and computer-readable media for dynamic prefetching for database queries are disclosed. A query of a database is started according to a first prefetch policy. Before completing the query, the first prefetch policy is changed to a second prefetch policy. A portion of the query is performed according to the second prefetch policy.

Abstract: Updates for transactions to a replication log for a database may be amortized. As updates are received as part of an active transaction, replication log records may be generated. When the size of replication log records exceeds a transaction size threshold, the replication log records may be stored in a remote data store instead of a local data store. When a request to commit the active transaction is received, an replication log for the database may be updated to include the replication log records from a transaction data object in the remote data store.

Abstract: Methods, systems, and computer-readable media for dynamic prefetching for database queries are disclosed. A query of a database is started according to a first prefetch policy. Before completing the query, the first prefetch policy is changed to a second prefetch policy. A portion of the query is performed according to the second prefetch policy.

Abstract: Techniques for a context preservation during server restart are described. A restart of a database server having at least one open communications session with a database client is initiated. The database server can be executed by a compute instance hosted by a computer system of a provider network. A restarted database server is launched. The restarted database server obtains session state data to resume the at least one open communications session with the database client, the session state data including one or more session variables. The restarted database server receives a transaction from the database client.

Abstract: Storage level query processing may be implemented for processing database queries. Nodes that can access a database may perform parallel processing for at least a portion of a database query. An indication may be received that specifies parallel processing for the database query. The nodes can then be caused to perform the portion of the query as part of providing a result in response to the database query instead of a node, such as a query engine node, that received the database query.

Abstract: Automatic consistency is implemented for forwarding writes in a database system. A read-only node may support both read and write requests to a database. The read only node may forward write requests to a read-write node. The read-only node may determine whether to include the forwarded requests in a version of the database for a read request automatically according to a consistency specified for a read request.

Abstract: A hybrid query engine using different query engines may be implemented to provide access to a database. A database query to a database may be received at a hybrid query engine. A plan to perform the database query may be generated that when performed by the hybrid query engine causes one query engine to perform an assigned portion of the plan by accessing data that describes the database. Another portion of the plan assigned to another query engine may be performed by the hybrid query engine to cause the other query engine to perform the other portion of the plan by accessing the same data that describes the database.

Abstract: Transactional scans of portions of a database may be performed. When a query is received that causes a scan of a database, different portions of the database may be scanned within separate transactions. Operations applicable to perform the scan the records of the different portions of the database may be invoked once within the transactions instead of invoking the operations individually for each of the records in the different portions. Results of the query based on the scanned portions may then be provided in response to the query.

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 method and system for handling foreign key database updates. The database includes one or more tables where each table includes at least one row and a primary key or foreign key. The method and system include evaluating a list of row operations for foreign key relationships. After evaluating the foreign key relationships, the tables determined to have acyclic foreign key relationships are grouped into a first set of tables and the tables determined to have cyclic foreign key relationships are grouped into a second set of tables. The method and system further include ordering the first set of tables into a list based on the foreign key relationships among the set of tables, such that a parent table will be processed before a child table. The row operations are then applied to each table in the list in the specified order.

Abstract: A method and system for transparently caching and reusing database query execution plans. The method and system include caching a first query that contains a first constant. A first query is associated with an execution plan that represent the first constant with a parameter name. The method and system further include receiving a new query that contains a second constant and comparing the new query with the first query. A match is determined to exist even when the second constant fails to match the first constant.

Abstract: A method and system for handling foreign key database updates. The database includes one or more tables where each table includes at least one row and a primary key or foreign key. The method and system include evaluating a list of row operations for foreign key relationships. After evaluating the foreign key relationships, the tables determined to have acyclic foreign key relationships are grouped into a first set of tables and the tables determined to have cyclic foreign key relationships are grouped into a second set of tables. The method and system further include ordering the first set of tables into a list based on the foreign key relationships among the set of tables, such that a parent table will be processed before a child table. The row operations are then applied to each table in the list in the specified order.

Abstract: A method and system for handling foreign key database updates. The database includes one or more tables where each table includes at least one row and a primary key or foreign key. The method and system include evaluating a list of row operations for foreign key relationships. After evaluating the foreign key relationships, the tables determined to have acyclic foreign key relationships are grouped into a first set of tables and the tables determined to have cyclic foreign key relationships are grouped into a second set of tables. The method and system further include ordering the first set of tables into a list based on the foreign key relationships among the set of tables, such that a parent table will be processed before a child table. The row operations are then applied to each table in the list in the specified order.

Abstract: A computer-implemented component broker series server for optimized caching of SQL data is implemented. In an object-oriented computer system, relational data from a relational database is cached in a data cache. The object-oriented computer system has a server that includes an instance manager and that is connected to at least one client. Objects that represent the relational data are created and managed under control of the instance manager. The relational data is stored in the data cache, which includes a virtual memory data cache for each client.