JobHistory_Upd - performance fix #1668
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The performance optimization for MAX(instance_id) is subject to plan variation. Changing the OUTER APPLY to use TOP(1) instead of MAX should allow us to get the query plan we want more reliably.
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Pull request overview
This PR optimizes the performance of the JobHistory_Upd stored procedure by improving how the maximum instance_id is retrieved from partitioned data. The change replaces a MAX(instance_id) aggregation with a TOP(1)... ORDER BY instance_id DESC pattern to achieve more predictable query plan generation that efficiently seeks on InstanceID within each partition and performs a backward ordered scan.
Key Changes:
- Replaced
MAX(instance_id)withTOP(1) instance_id ORDER BY instance_id DESCin the OUTER APPLY subquery - Added inline documentation explaining the performance optimization strategy
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The performance optimization for MAX(instance_id) is subject to plan variation. Changing the OUTER APPLY to use TOP(1) instead of MAX should allow us to get the query plan we want more reliably.