When managing large-scale data, especially in partitioned tables, choosing the right data modification strategy is crucial. This article explores why MERGE INTO with the Merge-on-Read (MOR) strategy is often more advantageous than INSERT OVERWRITE, particularly as partitioning schemes evolve.​

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Apache Iceberg's MERGE INTO with Merge-on-Read strategy provides significant advantages over INSERT OVERWRITE for data lake operations. MERGE INTO offers up to 66% cost savings by only modifying affected rows rather than rewriting entire partitions, reduces I/O operations, and handles partition evolution more gracefully. The approach is particularly effective for incremental loads, CDC, and slowly changing dimensions, though proper compaction maintenance is essential for long-term performance.

Why You Should Prefer MERGE INTO Over INSERT OVERWRITE in Apache Iceberg

Understanding MERGE INTO vs. INSERT OVERWRITE