Three Idempotent Write Patterns

Concepts covered: paIdempotentWrites, paPartitionOverwrite

Three write patterns cover the vast majority of idempotent batch pipelines. Partition overwrite replaces a slice of the destination table identified by a partition key. MERGE matches incoming rows to existing rows by a business key and updates or inserts as appropriate. DELETE-then-INSERT inside a transaction clears a logical slice and writes its replacement atomically. Each pattern has a niche, and a senior engineer reaches for the right one without thinking. Reaching for the wrong one produces pipelines that are technically idempotent but operationally awkward. The names of the three patterns are not standardized across the industry; one team's UPSERT is another team's MERGE is another team's DELETE-then-INSERT is another team's INSERT OVERWRITE. The conceptual shapes below are stable ac

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