When you set up unique key constraints on the SQL table, Azure Stream Analytics removes duplicate records. It splits the data into batches and recursively inserts the batches until a single duplicate record is found. The split and insert process ignores the duplicates one at a time. For a streaming job that has many duplicate rows, the process is inefficient and time-consuming. If you see multiple key violation warning messages in your Activity log for the previous hour, it's likely that your SQL output is slowing down the entire job.
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