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Performance overhead of SQL user-defined functions

Some time ago I wrote an article that described the performance tradeoffs one encounters when using SQL user-defined functions – sometimes called UDFs or PSM (Persistent Stored Module) functions – from within an SQL query. In that article, I wrote: A recent email exchange with software consultant Breck Carter regarding the performance of user-defined functions

 
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Why the SQL Standard does not need another way to do GROUP BY

In a recent article, Lukas Eder proposed enhancements to the SQL Standard’s GROUP BY syntax to include support for implicit grouping attributes, such as that provided by the Cypher query language. I applaud Lukas’ efforts to define useful changes to the SQL language, but I am going to try to show in this article that

 
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JPA and native SQL queries – part deux

In a previous article I outlined how one can use JPA’s @SqlResultMapping annotation to permit one to utilize JPA’s createNativeQuery() method and map an SQL native query to a result set composed of something other than JPA-managed object instances. In this follow-on article I’ll comment on a recent JPA extension to the @SqlResultMapping annotation, the

 
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JPA and native SQL queries – part un

Hibernate is by far the most popular of the various object-relational mapping tools available for Java, and is one of the ORM toolkits that supports the Java Persistence API, which forms part of the Java EE 7 specification. The current JPA specification version is 2.1 (released April 2013), and you can find the specification for

 
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The peril of complexity

In June 2011 I gave the keynote talk at the 2011 DBTEST Workshop in Athens, Greece, which was co-located with the 2011 ACM SIGMOD conference. Here, I have re-posted the slides of my talk, entitled The Peril of Complexity. In the talk, I outline some of the software engineering issues faced by relational database vendors

 
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Set-level operations do matter

A recent email exchange with software consultant Breck Carter regarding the performance of user-defined functions in SQL has prompted me to re-post this article that I originally wrote in 2008. User-defined functions in SQL have their uses; unfortunately their performance characteristics are highly variable because it is very difficult impossible for a query optimizer to

 
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The first deadly sin

In this semester I’m teaching two SQL fundamentals courses, one with MySQL and one with Microsoft SQL Server. We are quickly reaching the point where the notions of query equivalence and support for domains will be necessary – and that reminded me of this blog post that I wrote last spring while I was still

 
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