David Rowley <david.row...@2ndquadrant.com> writes: > I looked over this and only noted down one thing:
> In estimate_path_cost_size, can you explain why list_concat_copy() is > needed here? I don't see remote_param_join_conds being used after > this, so might it be better to just get rid of remote_param_join_conds > and pass remote_conds to classifyConditions(), then just > list_concat()? Hm, you're right, remote_param_join_conds is not used after that, so we could just drop the existing list_copy() and make it remote_conds = list_concat(remote_param_join_conds, fpinfo->remote_conds); I'm disinclined to change the API of classifyConditions(), if that's what you were suggesting. >> It turns out there are a *lot* of places where list_concat() callers >> are now leaking the second input list (where before they just leaked >> that list's header). So I've got mixed emotions about the choice not >> to add a variant function that list_free's the second input. > In some of these places, for example, the calls to > generate_join_implied_equalities_normal() and > generate_join_implied_equalities_broken(), I wonder, since these are > static functions if we could just change the function signature to > accept a List to append to. I'm pretty disinclined to do that, too. Complicating function APIs for marginal performance gains isn't something that leads to understandable or maintainable code. > If we do end up with another function, it might be nice to stay away > from using "concat" in the name. I think we might struggle if there > are too many variations on concat and there's a risk we'll use the > wrong one. If we need this then perhaps something like > list_append_all() might be a better choice... I'm struggling to build > a strong opinion on this though. (I know that because I've deleted > this paragraph 3 times and started again, each time with a different > opinion.) Yeah, the name is really the sticking point here; if we could think of a name that was easy to understand then the whole thing would be much easier to accept. The best I've been able to come up with is "list_join", by analogy to bms_join for bitmapsets ... but that's not great. regards, tom lane