Unnest is a common operation in Facebook’s daily Presto workload. It converts an ARRAY, MAP, or ROW into a flat relation. Its original implementation used deep copy all the time and was very inefficient. In Unnest Operator Performance Enhancement with Dictionary Blocks, the author improved the Unnest operator by up to 10x in CPU and…
A common type of spatial query involves relating one table of geometric objects (e.g., a table population_centers with columns population, latitude, longitude) with another such table (e.g., a table counties with columns county_name, boundary_wkt), such as calculating for each county the population sum of all population centers contained within it. These kinds of calculations are…