Details

    • Type: Sub-task
    • Status: Resolved
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: 2.1.0
    • Fix Version/s: 2.2.0
    • Component/s: SQL
    • Labels:
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    • Target Version/s:

      Description

      This JIRA is a sub-task of SPARK-17626.

      The objective is to provide a consistent performance improvement for star schema queries. Star schema consists of one or more fact tables referencing a number of dimension tables. In general, queries against star schema are expected to run fast because of the established RI constraints among the tables. This design proposes a join reordering based on natural, generally accepted heuristics for star schema queries:

      • Finds the star join with the largest fact table and places it on the driving arm of the left-deep join. This plan avoids large tables on the inner, and thus favors hash joins.
      • Applies the most selective dimensions early in the plan to reduce the amount of data flow.

      The design description is included in the below attached document.


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        1. StarJoinReordering1214.doc
          491 kB
          Ioana Delaney

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              • Assignee:
                ioana-delaney Ioana Delaney
                Reporter:
                ioana-delaney Ioana Delaney
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