I see a lot of people want to talk about #PostgreSQL things that go wrong with stuff I wrote. When autovacuum goes wrong; how multixacts require extra table freezing; bgworkers handle signals wrong.
Today: "subtransactions -- can go wrong badly".
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People often overattribute problems in this area to an underlying general design. The implementation itself may well be improved within the confines of an old design, though. My argument is usually harder to make, and less pithy, but that tells us nothing about what really works.
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In this particular context (Subtrans SLRU), if we just allow configuring its size and increase it (from 32 pages to 1 MiB or so), it will hardly help... gitlab.com/postgres-ai/po
But maybe there are other ways to improve without changing design
cc
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Seems quite possible. How many times has anybody seriously analyzed the problems around subtransactions in this kind of detail before now? Sometimes all you really need is the proper motivation.