Re: Re: [PATCHES] Select parser at runtime

Ian Lance Taylor <ian(at)airs(dot)com> writes:
> ... most of the cost will be paid by the people who care about
> it. (Not all of the cost, because some communication will be required
> when the parse tree nodes are changed.)

> Along these lines, I don't think Bruce's suggestion of modifications
> to the Postgres gram.y is a good idea, because it causes the Oracle
> parser to add an ongoing cost to the Postgres parser.

And managing grammar changes and parse-tree-node changes is not an
ongoing cost? I beg to differ. We do that a lot, and keeping multiple
grammar files in sync is not a pleasant prospect. (Look at ecpg ---
it's a major pain to keep it in sync with the main parser, even though
it only shares productions and not output code. Worse, I have zero
confidence that it actually *is* in sync.)

If the grammar changes are small and localized, I think Bruce's #ifdef
approach might well be the way to go. However, we're speculating in
a vacuum here, not having seen the details of the changes needed.

regards, tom lane