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  1. Core Server
  2. SERVER-91616

Ignore indexes with collation for all kinds of regex predicates. Behind a query knob.

    • Type: Icon: Improvement Improvement
    • Resolution: Fixed
    • Priority: Icon: Major - P3 Major - P3
    • 8.1.0-rc0, 8.0.0-rc10
    • Affects Version/s: None
    • Component/s: None
    • None
    • Query Optimization
    • Fully Compatible
    • v8.0

      SERVER-65260 introduces a change to avoid IXSCAN for regex predicates if the index has collation arguing that bounds cannot be tightened and COLLSCAN performs better. We've discovered a number of scenarios in which the unbounded IXSCAN is better than COLLSCAN (e.g. HELP-60129) so we want to (see HELP-60129 for discussion and details):

      1. stick to SERVER-65260's described change (ignore regex type)
      2. setup a query knob to disable the behaviour for customers whose workloads experience regressions as a result of this.

            Assignee:
            c.alonso@mongodb.com Carlos Alonso Pérez
            Reporter:
            c.alonso@mongodb.com Carlos Alonso Pérez
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              Created:
              Updated:
              Resolved: