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Lead with a complete plugin quick start and add task-oriented usage, troubleshooting, customization, and contribution guides. Preserve the broader plugin framing, correct conflicting contract guidance, support Agents folder reviews, and align repository validation. Convert existing sample references to clickable links without changing knowledge rules. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
26 lines
1.5 KiB
Markdown
26 lines
1.5 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [maintainsiftindex, sift, calcsums, flowfield, write-cost]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Choose MaintainSIFTIndex by read-write ratio
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> Contributions welcome — open a PR to refine or extend this article.
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## Description
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`MaintainSIFTIndex` on a key decides whether SQL Server maintains the SIFT indexed view as underlying rows change. With `Yes`, writes that affect the key or sum fields also maintain the indexed aggregate. With `No`, that SIFT indexed view is not maintained, so a compatible `CalcSums` or FlowField calculation is computed from the base table instead and may require scanning many rows. There is no deferred "first read rebuild" of the SIFT structure.
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## Best Practice
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Measure aggregate-read latency and write cost under realistic filters and volumes. Keep `MaintainSIFTIndex = true` when the maintained aggregate materially benefits frequent `CalcSums` or FlowField reads. Consider `false` when writes dominate and the less-frequent aggregate reads can tolerate calculation from the base table.
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See sample: [`choose-maintainsiftindex-by-read-write-ratio.good.al`](choose-maintainsiftindex-by-read-write-ratio.good.al).
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## Anti Pattern
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Leaving `MaintainSIFTIndex = Yes` on every key by reflex or convenience. On write-heavy tables the cumulative cost turns every INSERT or MODIFY into several additional aggregate updates, and the impact compounds in batch imports and posting routines — often without any code-review signal that the property is the cause.
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