Hi, On 2019-03-03 13:29:04 -0500, Tom Lane wrote: > The cases I've been looking at suggest to me that we'd make far > more progress on the excessive-palloc'ing front if we could redesign > things to reduce unnecessary copying of parsetrees. Right now the > planner does an awful lot of copying because of fear of unwanted > modifications of multiply-linked subtrees. I suspect that we could > reduce that overhead with some consistently enforced rules about > not scribbling on input data structures; but it'd take a lot of work > to get there, and I'm afraid it'd be easily broken :-(
Given the difficulty of this tasks, isn't your patch actually a *good* attack on the problem? It makes copying lists considerably cheaper. As you say, a more principled answer to this problem is hard, so attacking it from the "make the constant factors smaller" side doesn't seem crazy? Greetings, Andres Freund
