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29 lines
1.4 KiB
Markdown
29 lines
1.4 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [calcsums, sift, sum, aggregate, totals]
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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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# Use CalcSums to aggregate filtered sets
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> Contributions welcome — open a PR to refine or extend this article.
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## Description
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When the task is to compute a sum over a filtered set, CalcSums lets the platform push the aggregation down to SQL using SIFT indexes. Iterating rows in AL to accumulate a total transports every row's data to the runtime only to discard it after adding one field. On ledger-entry-scale tables this difference is dramatic. The same SIFT infrastructure backs Sum-style FlowFields; when the value you need is already declared as a FlowField, calling CalcSums on the underlying table with the correct filters produces the same aggregate.
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## Best Practice
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Set the required filters on the record, then call CalcSums on the field you want aggregated. Ensure the table has a key whose SumIndexFields includes the summed field and whose key prefix matches the filters (see add-sift-keys-for-flowfields).
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See sample: `use-calcsums-for-flowfield-totals.good.al`.
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## Anti Pattern
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Looping a filtered set with FindSet and adding a field to an accumulator on every iteration performs work in AL that SQL already knows how to do in one aggregate query.
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See sample: `use-calcsums-for-flowfield-totals.bad.al`.
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