Re: Speaking of breaking compatibility...standard_conforming_strings

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

"David G. Johnston" <david.g.johnston@gmail.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".