I dig into a non-trivial Polybase query:
Polybase offers the ability to create statistics on tables, the same way that you would on normal tables. There are a few rules about statistics:
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Stats are not auto-created. You need to create all statistics manually.
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Stats are not auto-updated. You will need to update all statistics manually, and currently, the only way you can do that is to drop and re-create the stats.
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When you create statistics, SQL Server pulls the data into a temp table, so if you have a billion-row table, you’d better have the tempdb space to pull that off. To mitigate this, you can run stats on a sample of the data.
Round one did not end on a high note, so we’ll see what round two has to offer.