International Business Machines Corporation

John Frederick Hornibrook

Calisto Paul Zuzarte

Vincent Corvinelli

Qi Cheng

Bingjie Miao

Daniele Costante Zilio

Ian R Finlay

Ting Yu Leung

Xin Wu

Daniel Costante Zilio

Ivan Popivanov

Tam Minh Dai Tran

Yuri Deigin

Adam J Storm

Bruce Gilbert Lindsay

Eugene Jon Shekita

Eileen Tien Lin

Walid Rjaibi

Honesty Cheng Young

Sumit Negi

Jyh-Herng Chow

David C Sharpe

Laurent Sebastien Mignet

Amit Radheshyam Somani

Miroslaw Adam Flasza

Dimple Bhatia

Michael Joshua Snowbell

Dieu Quang La

Xiaoyan Qian

Edward Gust Branish, Ii

John E Lumby

Wing Yan Lau

William R Minor

Geoffrey Peddle

Jose A Saborit

Surendra Kumar Verma

Harold Hotelling Lee

Michael Arthur Franciscus Stuy

A method, system and computer program product includes receiving and parsing an SQL query, identifying at least one common sub expression, or sub-query, or combination thereof, used multiple times within the SQL query, constructing for the at least one common sub expression, or sub-query, or combination thereof, a query execution plan that maintains as part of an initial result set a bit vector for a fact table, storing a result bit vector and an indicator that tracks a last valid tuple processed to produce the result bit vector when a TEMP operation is indicated in the query execution plan, reassessing a TEMP result in other portions of the query execution plan, priming a list of tuples using the TEMP result, and retrieving respective columns for further processing in the query execution plan.

Reducing temp size over a base table

Techniques are disclosed for generating statistical views in a database system. In one embodiment, a request is received to execute a database workload. One or more constraints pertaining to executing the database workload is retrieved. The database workload is evaluated to generate multiple statistical view candidates. The statistical view candidates are refined based on the one or more constraints. One or more statistical views are then generated based on the refined statistical view candidates.

Generating statistical views in a database system

A method, computer program product, and system for optimizing aggregate queries are provided. The method, computer program product, and system provide for receiving an aggregate query comprising a GROUP BY operation and an aggregate function, creating an access plan for executing the aggregate query, the access plan including a join between an outer relation and an inner relation, and designating the join included in the access plan as an early out join.

Optimization of aggregate queries in database management systems using an early out join when processing min and max functions

A method and system for collecting statistics on database tables. In one embodiment, the method includes identifying a plurality of tables for statistics collection, wherein each table of the plurality of tables are remote tables; examining at least one attribute for each table identified for statistics collection; prioritizing the tables for statistics collection based on the at least one attribute; and collecting statistics on the identified tables in a priority sequence.

Statistics collection for database tables

In accordance with aspects of the present invention, provided are systems and computer program products for incrementally estimating the cardinality of a derived relation including statistically correlated partially applicable predicates for a range-partitioned table. During the generation of a QEP a cardinality estimate is calculated in which one or more partially applicable predicates is correlated to another partially applicable predicate and/or to one or more fully applicable predicates. The cardinality includes a number of rows expected to be returned by the QEP and is computed in an incremental fashion for each operator of the QEP.

Systems and computer program product for cost estimation using partially applied predicates

Methods and apparatus, including computer program products, implementing and using techniques for executing a query in a computer to retrieve data from a relational database stored on a data storage device. A query is received that contains a CASE expression having one or more subqueries. A query execution plan is generated. The query execution plan uses a parameterized union all operator to keep the semantics of the CASE expression, and a nested loop join operator to drive data across the section of the query execution plan that executes the CASE expression without performing any join operations. The generated query execution plan is executed in the computer to retrieve data from the relational database.

Executing CASE expressions containing subqueries

A workload specification is obtained for the database. Based on the workload specification, candidate ones of the tables are identified and ranked. Compression impact is evaluated for the candidate ones of the tables. A design for the database is developed, specifying at least one of: (i) which of the tables should be compressed, and (ii) which of the tables should not be compressed.

Method for automated design of row compression on tables in a relational database

In accordance with aspects of the present invention, provided are methods for incrementally estimating the cardinality of a derived relation including statistically correlated partially applicable predicates for a range-partitioned table. During the generation of a QEP a cardinality estimate is calculated in which one or more partially applicable predicates is correlated to another partially applicable predicate and/or to one or more fully applicable predicates. The cardinality includes a number of rows expected to be returned by the QEP and is computed in an incremental fashion for each operator of the QEP.

Methods of cost estimation using partially applied predicates

A system for estimating cardinalities for a plurality of columns in a database system is disclosed. The system include obtaining statistics collected for the plurality of columns. A first portion of the statistics indicates at least one relationship between at least a portion of the plurality of columns, while a second portion of the statistics includes single column statistics. The system also include utilizing the first portion and the second portion of the statistics to estimate the cardinality for the plurality of columns.

System for estimating cardinality in a database system

A system and method are provided for updating database statistics for use in generating query execution plans. A first query for a database is received, for example by a compiler, and the compiler accesses statistics associated with the first query for optimizing a query execution plan for the first query. The statistics may be accessed from a first cache. If the statistics retrieved from the first cache are determined to be stale, the system obtains updated statistics and may store them in a temporary cache. The stale statistics in the first cache are marked as invalid. Existing queries using the first cache may continue to use the first cache, while new queries may be provided with updated statistics.

Optimized collection of just-in-time statistics for database query optimization

A method and system for estimating cardinalities for a plurality of columns in a database system is disclosed. The method and system include obtaining statistics collected for the plurality of columns. A first portion of the statistics indicates at least one relationship between at least a portion of the plurality of columns, while a second portion of the statistics includes single column statistics. The method and system also include utilizing the first portion and the second portion of the statistics to estimate the cardinality for the plurality of columns.

Method and system for estimating cardinality in a database system

The present system improves the performance of a query in a database system when a plan for the query comprises sorting an input that is at least partially sorted such that a slow materialization sort can be applied. The invention applies the slow materialization sort by determining a sequence of subsets in accordance with the partially sorted input. As each of the subsets is determined, the subset is output for further processing. Advantageously, the invention reduces the waiting period for obtaining results from a sorting operation under certain circumstances.

System and method for slow materialization sorting of partially ordered inputs in a database system

A system and process for evaluating the performance of an operational database system without interfering with the normal operation of the operational database system is described. The process involves the creation of a test database which contains the system catalogs of the operational database system as user tables. The test database is used to compile queries using these simulated system catalogs. The access plan generated by the compilation in the test database can then be used to evaluate the performance of the queries.

System and process for evaluating the performance of a database system

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Markham, Canada

John Frederick Hornibrook