Query Shredding: Efficient Relational Evaluation of Queries over Nested Multisets

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Nested relational query languages have been explored extensively, and underlie industrial language-integrated query systems such as Microsoft's LINQ. However, relational databases do not natively support nested collections in query results. This can lead to major performance problems: if programmers write queries that yield nested results, then such systems typically either fail or generate a large number of queries. We present a new approach to query shredding, which converts a query returning nested data to a fixed number of SQL queries. Our approach, in contrast to prior work, handles multiset semantics, and generates an idiomatic SQL:1999 query directly from a normal form for nested queries. We provide a detailed description of our translation and present experiments showing that it offers comparable or better performance than a recent alternative approach on a range of examples.
Original languageEnglish
Title of host publicationProceedings of the 2014 ACM SIGMOD International Conference on Management of Data
Number of pages12
ISBN (Print)978-1-4503-2376-5
Publication statusPublished - 18 Jun 2014
EventThe 2014 ACM SIGMOD International Conference - Snowbird, United States
Duration: 22 Jun 201427 Jun 2014


ConferenceThe 2014 ACM SIGMOD International Conference
Abbreviated titleSIGMOD 2014
Country/TerritoryUnited States


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