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The plugin is used when you want to calculate some basic aggregations in your data similar to what you could do with a window function in SQL.
BigQuery ELT Transformation Pushdown (6.9.0+)
Window aggregation stages are now eligible to execute in BigQuery when BigQuery ELT Transformation Pushdown is enabled in a pipeline. Window aggregation stages will be executed in BigQuery when a preceding stage has already been executed in BigQuery (such as a Join operation or another aggregation stage) or if the source is BigQuery. All the above mentioned functions are supported in BigQuery.
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