bcquality/microsoft/knowledge/performance/choose-maintainsiftindex-by-read-write-ratio.md

bc-version	domain	keywords	technologies	countries	application-area
all	performance	maintainsiftindex sift calcsums flowfield write-cost	al	w1	all

Choose MaintainSIFTIndex by read-write ratio

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Description

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.

Best Practice

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.

See sample: choose-maintainsiftindex-by-read-write-ratio.good.al.

Anti Pattern

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.