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Type: Improvement
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Resolution: Fixed
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Priority: Major - P3
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Affects Version/s: None
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Component/s: None
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None
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Query Optimization
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Fully Compatible
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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):
- stick to
SERVER-65260's described change (ignore regex type) - setup a query knob to disable the behaviour for customers whose workloads experience regressions as a result of this.
- fixes
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SERVER-65260 An index with non-simple collation should not be considered for predicates with a regex value
- Closed