Re: Speaking of breaking compatibility...standard_conforming_strings

On Tue, May 24, 2016 at 3:57 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> > I just noticed this comment in scan.l:
> > /*
> > * GUC variables. This is a DIRECT violation of the warning given at the
> > * head of gram.y, ie flex/bison code must not depend on any GUC
> variables;
> > * as such, changing their values can induce very unintuitive behavior.
> > * But we shall have to live with it as a short-term thing until the
> switch
> > * to SQL-standard string syntax is complete.
> > */
> > int backslash_quote = BACKSLASH_QUOTE_SAFE_ENCODING;
> > bool escape_string_warning = true;
> > bool standard_conforming_strings = true;
>
> > I'm not exactly sure what else needs to happen to remove these forbidden
> > GUCs and if we are not prepared to do this now when will we ever be...
>
> Dunno, are you prepared to bet that nobody is turning off
> standard_conforming_strings anymore?
>
> In any case, we keep adding new violations of this rule (cf
> operator_precedence_warning) so I have little hope that it will ever be
> completely clean.
>

​I tend to hold the same position. I'd probably update the last sentence
of the comment to reflect that reality.

"We use them here due to the user-facing capability to change the parsing
rules of SQL-standard string literals​."

The switch is not likely to ever be "complete" and if so not likely in
whatever period the future reader might consider "short-term".

​David J.
​