sp_IndexCleanup: fix #721 unique constraint subset + replace ISNULL schema join#722
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erikdarlingdata merged 1 commit intodevfrom Mar 25, 2026
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…ULL schema join Issue #721: Unique constraints were excluded from both sides of the Key Subset rule, so a NC index that was a prefix of a UC's keys was never flagged. Removed the NOT EXISTS check on the wider (target) side so UCs can serve as the superset target. The narrower-side check stays to prevent disabling UCs themselves. Schema join: Replaced LEFT JOIN sys.tables + LEFT JOIN sys.views + ISNULL(t.schema_id, v.schema_id) with a single JOIN sys.objects in all 4 query locations. Eliminates the non-SARGable ISNULL predicate that caused late filtering in the optimizer. Also scoped #usage_stats staging to #filtered_objects. Tested on SQL2022 (repro from #721 confirmed fixed) and SQL2016. Closes #721 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Bug fix (#721): Unique constraints can now serve as the superset target in Key Subset detection. Previously both sides were excluded from the rule, so a NC index with keys that were a prefix of a UC's keys was never flagged.
Schema join: Replaced
LEFT JOIN sys.tables + LEFT JOIN sys.views + ISNULL(t.schema_id, v.schema_id)withJOIN sys.objectsin all 4 query locations. Eliminates non-SARGable predicate.Test plan
IX_tbl_owntesttable_OrgunitID_PersIDcorrectly flagged as Key Subset ofUI_tbl_owntesttableCloses #721
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