Re: Changing SQL Inlining Behaviour (or...?)

> * Solution #2 - Quick and dirty and invisible. Tom suggested a hack that achieves the aims of #1 but without adding syntax to CREATE FUNCTION: have the inlining logic look at the cost of the wrapper and the cost of parameters, and if the cost of the wrapper "greatly exceeded" the cost of the parameters, then inline. So the PostGIS project would just set the cost of our wrappers very high, and we'd get the behaviour we want, while other users who want to use wrappers to force caching of calculations would have zero coded wrapper functions.  Pros: Solves the problem and easy to implement, I'm happy to contribute. Cons: it's so clearly a hack involving hidden (from users) magic.
> ...
> So my question to hackers is: which is less worse, #1 or #2, to implement and submit to commitfest, in case #3 does not materialize in time for PgSQL 12?

I've been working with Paul to create and test a patch (attached) that
addresses Solution #2. This patch essentially modifies the inlining
logic to compare the cost of the function with the total cost of the
parameters. The goal as stated above, is that for these kinds of
functions, they would be assigned relatively high cost to trigger the
inlining case.