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Postgres Foreign Data Wrappers and fdw_tuple_cost

Umair Shahid provides background info on a recent change:

“Why is DEFAULT_FDW_TUPLE_COST so insanely low?”

That was the subject of the email thread initiated by David Rowley to discuss this topic. I found the subject line amusing, accurate, and fully descriptive of the problem at hand. The discussion resulted in a commit that changed the default value from 0.01 to 0.2. Because I had previously written about postgres_fdw and also mentioned fdw_tuple_cost, I figured it would be good to go deeper into what this parameter is about and why it makes sense to default it to 0.2.

Read on to learn more about Foreign Data Wrappers (the Postgres equivalent to PolyBase in SQL Server), tuple costing, and more.