Derby
  1. Derby
  2. DERBY-4327

Implement optimizer support for bushy trees.

    Details

    • Type: Improvement Improvement
    • Status: Open
    • Priority: Major Major
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: SQL
    • Urgency:
      Normal
    • Bug behavior facts:
      Performance, Seen in production

      Description

      Currently, the optimizer only considers left-deep trees. For queries involving many tables, the best plan may be bushy. In this email thread, a user notes poor performance by Derby on queries involving 5 or more tables: http://www.nabble.com/Slow-performance-on-5-or-more-joins-in-a-star-schema-tt24708686.html

        Issue Links

          Activity

          Hide
          Nirmal Fernando added a comment -

          Hi,

          I am really interested in this issue! I am wondering whether this is a suitable project as a GSoC project?

          Thanks!

          Show
          Nirmal Fernando added a comment - Hi, I am really interested in this issue! I am wondering whether this is a suitable project as a GSoC project? Thanks!
          Hide
          Rick Hillegas added a comment -

          Hi Nirmal,

          My sense is that this is a tricky issue with a large risk of destabilizing existing applications. The fallout from this change would be felt over many subsequent releases. I would not recommend this as a GSoC project or as someone's first introduction to the Derby optimizer. Thanks.

          Show
          Rick Hillegas added a comment - Hi Nirmal, My sense is that this is a tricky issue with a large risk of destabilizing existing applications. The fallout from this change would be felt over many subsequent releases. I would not recommend this as a GSoC project or as someone's first introduction to the Derby optimizer. Thanks.
          Hide
          Nirmal Fernando added a comment -

          Hi Rick,

          Thanks for the reply!

          Show
          Nirmal Fernando added a comment - Hi Rick, Thanks for the reply!
          Show
          Dag H. Wanvik added a comment - - edited Some links: https://www.simple-talk.com/sql/performance/join-reordering-and-bushy-plans/ http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDwQFjAA&url=http%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fdownload%3Fdoi%3D10.1.1.56.6379%26rep%3Drep1%26type%3Dpdf&ei=3GUoUtbTN8uQ0QWh0oDYAw&usg=AFQjCNFme8BiQI59ZnxP68M6cnY0Pzr_cA&bvm=bv.51773540,d.d2k&cad=rja

            People

            • Assignee:
              Unassigned
              Reporter:
              Rick Hillegas
            • Votes:
              3 Vote for this issue
              Watchers:
              2 Start watching this issue

              Dates

              • Created:
                Updated:

                Development