International Business Machines Corporation

Thomas Owen McKinley

Robert J Bestgen

Thomas Paul Giordano

David Rolland Welsh

Michael W Cain

Richard Miles Rocheleau

Brian Robert Muras

Paul Reuben Day

Gary Ross Ricard

Daniel Beuch

Shantan Kethireddy

Mark John Anderson

Michael D Pfeifer

Kevin James Kathmann

David Glenn Carlson

Scott Forstie

David Lee Hermsmeier

James Michael Flanagan

Curtis Neal Boger

Robert Anthony Petrillo

Robert Paul Mech

Mukesh Rathor

Daniel Dean Bender

System, method, and computer program product to order query results, by processing a received query at least in part using a composite key index, wherein the composite key index comprises at least two key columns, wherein the at least two key columns comprise at least one pre-ordering column and an ordering column, wherein the query specifies ordering criteria to order a result set based on values of the ordering column, wherein the processing comprises receiving, from the composite key index, an ordering column value for each unique pre-ordering column value in the composite key index, identifying a first ordering column value as being ordered first according to the ordering criteria, and returning the first ordering column value as being responsive to the query.

Index merge ordering

Method to order query results, by processing a received query at least in part using a composite key index, wherein the composite key index comprises at least two key columns, wherein the at least two key columns comprise at least one pre-ordering column and an ordering column, wherein the query specifies ordering criteria to order a result set based on values of the ordering column, wherein the processing comprises receiving, from the composite key index, an ordering column value for each unique pre-ordering column value in the composite key index, identifying a first ordering column value as being ordered first according to the ordering criteria, and returning the first ordering column value as being responsive to the query.

A database query optimizer includes an access plan storage mechanism that stores execution detail corresponding to a query statement in an access plan cache. By storing execution detail in the access plan cache along with the query statement, the execution detail is available when needed to debug database problems, even after a problem occurs. The execution detail stored in the access plan cache may be mined and analyzed after-the-fact, producing a very powerful tool for debugging database problems. Snapshots of the execution detail may also be created by a user. In addition, the user may setup autonomic snapshots and comparisons so that a user may be alerted from a degradation in database performance between two snapshots.

Database execution detail repository

Database management systems and methods for searching a database are disclosed. In one embodiment, an inspector examines a plan cache or a program containing embedded queries. A plurality of similar queries is identified, and an alias is generated that satisfies the plurality of queries. The alias may be executed on a database to output a result set. Queries belonging to the alias may be executed on the result set of the alias, rather than on the database. Accordingly, efficiency is improved and runtime costs are reduced as compared to conventional database management systems.

Method of querying relational database management systems

An apparatus, program product and method represent a database query access plan a query execution data structure including a plurality of query node objects arranged into a tree relationship to define a parent node object and at least one child node object, and an attribute data structure that references a plurality of attributes utilized by the query execution data structure. At least one of the parent and child node objects includes an attribute operation data structure configured to manipulate at least a subset of the plurality of attributes in the attribute data structure by accessing the attribute operation data structure. By partitioning the functionality of a query access plan into a collection of node objects and an attribute data structure, and then providing within at least a subset of the node objects attribute operation data structures that manipulate the attribute data structure, the resulting query engine architecture becomes significantly extendible and adaptable. Moreover, through appropriate selection of attribute operations, and coding of such operations using directly executable program code, optimal query engine performance may also be obtained.

Object-oriented query execution data structure

A weak record locking scheme that, while enforcing serialization of record updates, permits a read to extract data from uncommitted updates. Specifically, records are locked in association with a process or thread performing a lock. When the records affected by a transaction are initially locked for reading or updating, they are locked at the process level. When a particular record is to be read or updated as part of a transaction, it is locked at the thread level. A read transaction that will accept uncommitted changes uses a weak lock to lock the record for reading. A weak lock may be made on a record so long as the record is not already locked for updating at the thread level. While a record is weakly locked for reading, it cannot be locked for updating at the thread level. A record may thus be weakly locked even though the record is locked for updating at the process level by the same process. Weak locking thus preserves serialization of updates, while reducing delays caused by locking conflicts.

Weak record locks in database query read processing

A method, memory system, and computer program product are provided for implementing lock based delayed space recycle control. The memory space recycle method is used with a memory in a computer system. A data element lock is obtained for a data record in a data block. Then an update on the data record is performed. A waiting to be recycled index for the data block is maintained. The waiting to be recycled index includes a record number, an address of the large object block (LOB) and the length of the LOB space. When the last lock on a data element is about to be released the waiting to be recycled areas associated with that data element are freed.

Method, memory system, and computer program product for implementing lock based delayed space recycle control

In parallel process computer systems multiple tasks are simultaneously executed. However, where resource contention exists, the multiple tasks become serialized, reducing system performance. Once such resource contention is arm contention during reads for files stored under multiple arms on direct access storage devices (DASDs). According to the preferred embodiment, a method is provided that assigns read tasks in a manner that reduces the probability of arm contention during the file reads. First, the plurality of extents storing the file are correlated to their associated arm. Second, for each of the plurality of arms, the attributes of extents under that arm, preferably including the extent read times, are accumulated. Finally, the plurality of simultaneous read tasks are assigned to the plurality of extents according to the accumulated attributes such that arms that have a greater need for service are favored over arms that have a lesser need when reading the file. Assigning the tasks in this manner lessons the probability of arm contention during file reads, increasing system performance.

Computer mechanism for reducing DASD arm contention during parallel

The present invention involves a database administrator that is comprised of a plurality of database managers and a plurality of database servers. The database managers act as an interface between the database servers and client programs and the database servers act as an interface between the database managers and the database itself. The client programs, database managers, and database servers all execute within a single-level-store environment, which allows them to communicate with one another without incurring the expense of inter-address space communication and/or the expense associated with the cross-address space mapping of query results.

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Rochester, MN, United States of America

Thomas Owen McKinley