On 2020-Jul-24, Andres Freund wrote: > I think the issue is more that we need to take into accoutn that the > overhead of JITing scales ~linearly with the number of JITed > expressions. And that's not done right now. I've had a patch somewhere > that had a prototype implementation of changing the costing to be > #expressions * some_cost, and I think that's a lot more accurate. I don't quite understand why is it that a table with 1000 partitions means that JIT compiles the thing 1000 times. Sure, it is possible that some partitions have a different column layout, but it seems an easy bet that most cases are going to have identical column layout, and so tuple deforming can be shared. (I'm less sure about sharing a compile of an expression, since the varno would vary. But presumably there's a way to take the varno as an input value for the compiled expr too?) Now I don't actually know how this works so please correct if I misunderstand it. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
