Towards Online and Transactional Relational Schema Transformations

L. Wevers, Matthijs Hofstra, Menno Tammens, Marieke Huisman, Maurice van Keulen

Research output: Book/ReportReportProfessional

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Abstract

In this paper, we want to draw the attention of the database community to the problem of online schema changes: changing the schema of a database without blocking concurrent transactions. We have identified important classes of relational schema transformations that we want to perform online, and we have identified general requirements for the mechanisms that execute these transformations. Using these requirements, we have developed an experiment based on the standard TPC-C benchmark to assess the behaviour of existing systems. We look at PostgreSQL, which does not support online schema changes; MySQL, which supports basic online schema changes; and pt-online-schema-change, which is a tool for MySQL that uses triggers to implement online schema changes. We found that none of the existing systems fulfill our requirements. In particular, existing non-blocking solutions can not maintain the ACID guarantees when composing schema transformations. This leads to intermediate states being exposed to database programs, which are non-trivial to handle correctly. As a solution direction, we propose lazy schema transformations, which can naturally be composed into complex schema transformations that properly guarantee the ACID properties, and which have minimal impact on concurrent transactions.
Original languageUndefined
Place of PublicationEnschede
PublisherCentre for Telematics and Information Technology (CTIT)
Number of pages19
Publication statusPublished - 3 Nov 2014

Publication series

NameCTIT Technical Report Series
PublisherUniversity of Twente, Centre for Telematics and Information Technology (CTIT)
No.TR-CTIT-14-10
ISSN (Print)1381-3625

Keywords

  • METIS-306090
  • EWI-25227
  • Transactions
  • Online
  • Non-blocking
  • Schema Transformations
  • Databases
  • IR-92355

Cite this

Wevers, L., Hofstra, M., Tammens, M., Huisman, M., & van Keulen, M. (2014). Towards Online and Transactional Relational Schema Transformations. (CTIT Technical Report Series; No. TR-CTIT-14-10). Enschede: Centre for Telematics and Information Technology (CTIT).
Wevers, L. ; Hofstra, Matthijs ; Tammens, Menno ; Huisman, Marieke ; van Keulen, Maurice. / Towards Online and Transactional Relational Schema Transformations. Enschede : Centre for Telematics and Information Technology (CTIT), 2014. 19 p. (CTIT Technical Report Series; TR-CTIT-14-10).
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Wevers, L, Hofstra, M, Tammens, M, Huisman, M & van Keulen, M 2014, Towards Online and Transactional Relational Schema Transformations. CTIT Technical Report Series, no. TR-CTIT-14-10, Centre for Telematics and Information Technology (CTIT), Enschede.

Towards Online and Transactional Relational Schema Transformations. / Wevers, L.; Hofstra, Matthijs; Tammens, Menno; Huisman, Marieke; van Keulen, Maurice.

Enschede : Centre for Telematics and Information Technology (CTIT), 2014. 19 p. (CTIT Technical Report Series; No. TR-CTIT-14-10).

Research output: Book/ReportReportProfessional

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PY - 2014/11/3

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N2 - In this paper, we want to draw the attention of the database community to the problem of online schema changes: changing the schema of a database without blocking concurrent transactions. We have identified important classes of relational schema transformations that we want to perform online, and we have identified general requirements for the mechanisms that execute these transformations. Using these requirements, we have developed an experiment based on the standard TPC-C benchmark to assess the behaviour of existing systems. We look at PostgreSQL, which does not support online schema changes; MySQL, which supports basic online schema changes; and pt-online-schema-change, which is a tool for MySQL that uses triggers to implement online schema changes. We found that none of the existing systems fulfill our requirements. In particular, existing non-blocking solutions can not maintain the ACID guarantees when composing schema transformations. This leads to intermediate states being exposed to database programs, which are non-trivial to handle correctly. As a solution direction, we propose lazy schema transformations, which can naturally be composed into complex schema transformations that properly guarantee the ACID properties, and which have minimal impact on concurrent transactions.

AB - In this paper, we want to draw the attention of the database community to the problem of online schema changes: changing the schema of a database without blocking concurrent transactions. We have identified important classes of relational schema transformations that we want to perform online, and we have identified general requirements for the mechanisms that execute these transformations. Using these requirements, we have developed an experiment based on the standard TPC-C benchmark to assess the behaviour of existing systems. We look at PostgreSQL, which does not support online schema changes; MySQL, which supports basic online schema changes; and pt-online-schema-change, which is a tool for MySQL that uses triggers to implement online schema changes. We found that none of the existing systems fulfill our requirements. In particular, existing non-blocking solutions can not maintain the ACID guarantees when composing schema transformations. This leads to intermediate states being exposed to database programs, which are non-trivial to handle correctly. As a solution direction, we propose lazy schema transformations, which can naturally be composed into complex schema transformations that properly guarantee the ACID properties, and which have minimal impact on concurrent transactions.

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Wevers L, Hofstra M, Tammens M, Huisman M, van Keulen M. Towards Online and Transactional Relational Schema Transformations. Enschede: Centre for Telematics and Information Technology (CTIT), 2014. 19 p. (CTIT Technical Report Series; TR-CTIT-14-10).