RQL: Retrospective computations over snapshot sets

Nikos Tsikoudis, Liuba Shrira, Sara Cohen

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations


Applications need to analyze the past state of their data to provide auditing and other forms of fact checking. Retrospective snapshot systems that support computations over data store snapshots, allow applications using simple data stores like Berkeley DB or SQLite, to provide past state analysis in a convenient way. Current snapshot systems however, offer no satisfactory support for computations that analyze multiple snapshots. We have developed a Retrospective Query Language (RQL), a simple declarative extension to SQL that allows to specify and run multi-snapshot computations conveniently in a snapshot system, using a small number of simple mechanisms defined in terms of relational constructs familiar to programmers. We describe RQL mechanisms, explain how they translate into SQL computations in a snapshot system, and show how to express a number of common analysis patterns with illustrative examples. We also describe how we implemented RQL in a simple way utilizing SQLite UDF framework in a Berkeley DB data store using Retro page-level incremental snapshot system. Multi-snapshot computations running over page-level incremental snapshots bring up interesting performance issues that have not been studied before. We present the first study defining a performance envelope for multi-snapshot computations over page-level incremental snapshots.

Original languageAmerican English
Title of host publicationAdvances in Database Technology - EDBT 2018
Subtitle of host publication21st International Conference on Extending Database Technology, Proceedings
EditorsMichael Bohlen, Reinhard Pichler, Norman May, Erhard Rahm, Shan-Hung Wu, Katja Hose
Number of pages12
ISBN (Electronic)9783893180783
StatePublished - 2018
Event21st International Conference on Extending Database Technology, EDBT 2018 - Vienna, Austria
Duration: 26 Mar 201829 Mar 2018

Publication series

NameAdvances in Database Technology - EDBT
ISSN (Electronic)2367-2005


Conference21st International Conference on Extending Database Technology, EDBT 2018

Bibliographical note

Publisher Copyright:
© 2018 Copyright held by the owner/author(s)


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