Abstract: At least one aspect of the present disclosure is directed to a systems and methods of maintaining key-value stores. The method can include establishing a first run of data records indexed by a key value. The method can include tracking, using an index, a merging of the data records of the first run onto a merge level on a database. The method can include establishing, concurrent to the merging of the first run, a second run of data records indexed by a key value. The method can include determining that the index tracking the merge of the data records of the first run onto the merge level satisfies a quantile condition. The method can include adding the subset of the second plurality of records of the second run to the merging of the first plurality of records of the first run onto the merge level maintained on the database.

Abstract: At least one aspect of the present disclosure is directed to a systems and methods of maintaining key-value stores. The method can include establishing a first run of data records indexed by a key value. The method can include tracking, using an index, a merging of the data records of the first run onto a merge level on a database. The method can include establishing, concurrent to the merging of the first run, a second run of data records indexed by a key value. The method can include determining that the index tracking the merge of the data records of the first run onto the merge level satisfies a quantile condition. The method can include adding the subset of the second plurality of records of the second run to the merging of the first plurality of records of the first run onto the merge level maintained on the database.

Abstract: Computer-implemented systems and associated operating methods take measurements and landmarks associated with robustness maps and perform tests evaluating the robustness of a database engine's operator implementations and/or query components. The illustrative computer-implemented system comprises logic that receives one or more robustness maps of measured database system performance acquired during database execution in a predetermined range of runtime conditions and uses information from the robustness map or maps to perform regression testing wherein landmarks in the robustness maps are operated upon as a robustness bugs describing conditions under which a predetermined implementation of a database operator or query component degrades in a manner different from a predetermined expected manner.

Abstract: Systems and methods for providing deferred lock enforcement for transactions are described. The method includes receiving a first request for access to a data resource for a transaction, assigning a first lock to the transaction, and receiving, from a candidate reader, a second request for access to the data resource. The method further includes determining an interpretation of the first lock as i) a first lock type responsive to determining that the transaction is in a read phase or ii) a second lock type responsive to determining that the transaction is in a commit processing phase, and assigning a second lock to the candidate reader responsive to interpreting the first lock as the first lock type, or declining to assign the second lock to the candidate reader responsive to interpreting the first lock as the second lock type.

Abstract: This disclosure provides systems, methods, and apparatus for managing locks for non-existing keys in an index of a database. The system can receive a first transaction for accessing a first requested key that does not match any of a plurality of keys in the index. The system partitions the first requested key using a partitioning function to a first partition. The system can also receive a second transaction for accessing a second requested key that does not match any of the plurality of keys in the index. The system also partitions the second requested key using the partitioning function to a second partition. The system assigns locks to the second transaction only if the second partition is distinct from the first partition.

Abstract: Systems and methods associated with page modification are disclosed. One example method may be embodied on a non-transitory computer-readable medium storing computer-executable instructions. The instructions, when executed by a computer, may cause the computer to fetch a page to a buffer pool in a memory. The page may be fetched from at least one of a log and a backup using single page recovery. The instructions may also cause the computer to store a modification of the page to the log. The modification may be stored to the log as a log entry. The instructions may also cause the computer to evict the page from memory when the page is replaced in the buffer pool. Page writes associated with the eviction may be elided.

Abstract: Systems and methods for providing deferred lock enforcement for transactions are described. The method includes receiving a first request for access to a data resource for a transaction, assigning a first lock to the transaction, and receiving, from a candidate reader, a second request for access to the data resource. The method further includes determining an interpretation of the first lock as i) a first lock type responsive to determining that the transaction is in a read phase or ii) a second lock type responsive to determining that the transaction is in a commit processing phase, and assigning a second lock to the candidate reader responsive to interpreting the first lock as the first lock type, or declining to assign the second lock to the candidate reader responsive to interpreting the first lock as the second lock type.

Abstract: Systems and methods associated with latch-free searching are disclosed. One example method includes receiving a key identifying data to be retrieved from a tree-based data structure. The method also includes performing a concurrent, latch-free search of the tree-based data structure until a leaf node is reached. The method also includes validating the leaf node. The method also includes retreading a portion of the search if the leaf node fails validation.

Abstract: Disclosed herein are a system, non transitory computer-readable medium, and method for estimating database performance. A request for an estimate of data is read. The estimate is calculated based at least partially on a node located in a data structure.

Abstract: This disclosure provides systems, methods, and apparatus for managing locks for non-existing keys in an index of a database. The system can receive a first transaction for accessing a first requested key that does not match any of a plurality of keys in the index. The system partitions the first requested key using a partitioning function to a first partition. The system can also receive a second transaction for accessing a second requested key that does not match any of the plurality of keys in the index. The system also partitions the second requested key using the partitioning function to a second partition. The system assigns locks to the second transaction only if the second partition is distinct from the first partition.

Abstract: This disclosure provides systems, methods, and apparatus for avoiding deadlocks in a database management system. The system includes a transaction engine that can receive query and update transactions for accessing a primary index and one or more related secondary indexes. The transaction engine requests the lock manager for locks for rows in the primary index and the related secondary indexes that the update and the query transactions need to access. For the query transaction, the transaction engine requests locks for the secondary index prior the requesting locks for the primary index. To avoid deadlocks, the transaction engine requests the locks for the update transaction in the same order as the requests for the query transaction.

Abstract: A data processing system performs query progress estimation based on processed value packets. In the illustrative data processing system, a database query processor comprises a query optimizer that creates a query plan, and a database plan executor that executes the query plan and observes intermediate result streams processed as the query plan is executed. A value packet manager anticipates value packets during query optimization, creates value packets as the intermediate result streams are processed, and compares anticipated value packets with created value packets to determine accuracy of the anticipated value packets and estimate query progress.

Abstract: Systems and methods associated with page modification are disclosed. One example method may be embodied on a non-transitory computer-readable medium storing computer-executable instructions. The instructions, when executed by a computer, may cause the computer to fetch a page to a buffer pool in a memory. The page may be fetched from at least one of a log and a backup using single page recovery. The instructions may also cause the computer to store a modification of the page to the log. The modification may be stored to the log as a log entry. The instructions may also cause the computer to evict the page from memory when the page is replaced in the buffer pool. Page writes associated with the eviction may be elided.

Abstract: Systems and methods associated with an at least partially sorted log archives are disclosed. One example method for restoring a database includes restoring members of a set of database pages originally stored on a failed media device in the database. Restoring a member of the set of pages includes loading an image of the member of the set of database pages from a backup. Restoring the member of the set of database pages also includes applying log entries associated with the member of the set of database pages to the image. The log entries may have been recorded after the image of the member of the set of database pages was taken. The log entries may be retrieved from the at least partially sorted log archive. Restoring the member of the set of database pages also includes writing the database page to a replacement media.

Abstract: Systems and methods associated with database transaction replay are described. In one example, a computer-readable medium may store computer-executable instructions. When executed by a computer, the instructions may cause the computer to prevent a database page from being written to a persistent portion of a database. The database page may be prevented from being written while there are uncommitted transactions associated with the database page. The instructions may also cause the computer to detect a system failure associated with the database. In response to the system failure, the instructions may cause the computer to analyze the database to identify a set of transactions that were committed and unwritten to the persistent portion when the system failure occurs. The instructions may cause the computer to then re-perform members of the set of transactions.

Abstract: An example data restoration approach includes loading a replacement storage media upon detecting a media failure in a failed storage media, detecting a request for data originally stored on the failed storage media that is pending restoration to the replacement storage media, and in response to detecting this data request, restoring a data segment associated with the data from a backup to the replacement storage media. The approach further modifies the data segment in the replacement storage media according to archived modifications to the data segment in a log archive and then responds to the data request.

Abstract: A method of implementing a tree data structure comprises creating a parent and child relationship between a first node and a second node, in which the first node and second node are at the same hierarchical level of the tree data structure, and maintaining only one incoming pointer for each of the nodes in the tree data structure at all times. A tree data structure in which each node in the tree data structure has a single incoming pointer, and in which the tree data structure comprises a pointer directed to a local overflow node from a node at the same hierarchical level as the local overflow node.

Abstract: A shiftable memory supporting in-memory data structures employs built-in data shifting capability. The shiftable memory includes a memory having built-in shifting capability to shift a contiguous subset of data from a first location to a second location within the memory. The shiftable memory further includes a data structure defined on the memory to contain data comprising the contiguous subset. The built-in shifting capability of the memory to facilitate one or more of movement of the data, insertion of the data and deletion of the data within the data structure.

Abstract: There is provided a computer-implemented method of dynamically reordering operations in a query plan. An exemplary method comprises processing a first set of tuples according to a first operation. The query plan is pipelined and specifies that the first operation generates input for a second operation. The query plan further specifies that the second operation is executed after the first operation. The computer-implemented method further includes determining that the second operation is to precede the first operation based on a specified policy. The computer-implemented method further includes executing the second operation for a second set of tuples before executing the first operation for the second set of tuples. The second operation generates an input for the first operation. The first operation is executed after the second operation.

Abstract: A system is disclosed for managing address reflectors. In one example, the system discloses a reflector storage 108, 116, 124, 608, with a set of reflector members 304 associated with a set of reflector names 306. The system also includes a computer 100, 604 programmed with executable instructions 500, 610 which operate a set of modules. The modules includes reflector management module 106, 114, 122 which, receives a character-string from user input 104, 120, and identifies the reflector names 306 whose reflector members 304 are partially defined by the character-string.