bcquality/microsoft/knowledge/performance/preserve-buffered-inserts-by-separating-target-reads.md

bc-version	domain	keywords	technologies	countries	application-area
all	performance	buffered-inserts bulk-inserts findlast insert target-table commit staging	al	w1	all

Keep eligible inserts together instead of re-reading their target

Description

Business Central can automatically buffer eligible Insert calls. Find/Calc on the target table, Modify/Delete on it, or Commit flushes pending inserts; consuming the Insert return value, or BLOB/AutoIncrement fields on the target, prevents buffering. A source-table read is not itself a target-table flush. There is no general InsertAll replacement for an AL loop.

Best Practice

When writing completed rows to an application-owned data-only table, allocate a collision-free run or range once, prepare every field before each Insert, and keep the insert sequence free of intervening target-table reads and writes. Let the owning business transaction determine the commit point. Trace called procedures and events as well as the visible loop; inspect actual SQL batches and writes, then test failures, retries, and any concurrent writers. The sample assumes an exclusive new run ID and no required trigger, validation, number-series, or subscriber effects. See sample: preserve-buffered-inserts-by-separating-target-reads.good.al.

Anti Pattern

Calling FindLast on the target for every row to allocate its next line number, inserting an incomplete row and immediately modifying it, or committing each iteration of an otherwise eligible insert sequence. Moving a shared FindLast out of the loop without concurrency-safe allocation is not a valid fix. Do not recommend skipping required triggers or persistence steps in sales documents, journals, or posting ledgers just to obtain buffering; repeated Modify calls do not automatically batch like eligible inserts. See sample: preserve-buffered-inserts-by-separating-target-reads.bad.al.

References

• Bulk inserts and flush/non-buffering conditions.
• Transaction checkpoints and restart safety.