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29 lines
1 KiB
Markdown
29 lines
1 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [isempty, count, findfirst, existence]
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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 IsEmpty for existence checks
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> Contributions welcome — open a PR to refine or extend this article.
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## Description
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IsEmpty is the cheapest way to answer whether at least one row matches the current filters. It short-circuits at the first match and never hydrates a record. Count() scans and counts the entire set; FindFirst fetches a full row just to be discarded.
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## Best Practice
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Use `if not Rec.IsEmpty() then ...` for existence checks. Reserve Count for cases where the exact number of rows is needed, and FindFirst for cases where you actually want the row's field values.
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See sample: `use-isempty-for-existence-checks.good.al`.
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## Anti Pattern
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`if Rec.Count() > 0` iterates the whole set just to answer a yes/no question. `if Rec.FindFirst() then` loads an entire row of data the caller never reads.
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See sample: `use-isempty-for-existence-checks.bad.al`.
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