Re: POC: converting Lists into arrays

On Mon, Feb 25, 2019 at 1:17 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'm not following your point here. If we change key data structures
> (i.e. parsetrees, plan trees, execution trees) to use some other list-ish
> API, that *in itself* breaks everything that accesses those data
> structures. The approach I propose here isn't zero-breakage, but it
> requires far fewer places to be touched than a complete API replacement
> would do.

Sure, but if you have third-party code that touches those things,
it'll fail to compile. With your proposed approach, there seems to be
a risk that it will compile but not work.

> Yup. So are you saying that we'll never redesign parsetrees again?
> We break things regularly, as long as the cost/benefit justifies it.

I'm mostly objecting to the degree that the breakage is *silent*.

> I completely disagree. Your proposal is probably an order of magnitude
> more painful than the approach I suggest here, while not really offering
> any additional performance benefit (or if you think there would be some,
> you haven't explained how). Strictly on cost/benefit grounds, it isn't
> ever going to happen that way.

Why would it be ten times more painful, exactly?

--
Robert Haas
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