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27 lines
1.2 KiB
Markdown
27 lines
1.2 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [findset, lock, locktable, readonly, update]
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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 FindSet in read-only mode by default
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## Description
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FindSet has two modes: FindSet() and FindSet(false) are read-only and take no update lock; FindSet(true) sets update-lock read isolation on the record before fetching. Update locks are expensive and hold for the lock scope, so passing `true` when you do not intend to modify the records increases contention under load.
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## Best Practice
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Call FindSet with no arguments when the loop only reads field values. Pass `true` only when the same loop is expected to call Modify, Delete, or Rename on the record, and the correctness of the operation depends on the matching rows being locked for the iteration.
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See sample: `use-findset-readonly-by-default.good.al`.
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## Anti Pattern
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Writing FindSet(true) reflexively for every iteration forces the platform to take a LockTable on every call, even when the loop only reads values. The older two-parameter signature `FindSet(ForUpdate, UpdateKey)` is obsolete and must not be used.
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See sample: `use-findset-readonly-by-default.bad.al`.
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