Re: Help needed with standard_conforming_strings

On Fri, 9 May 2008, Greg Sabino Mullane wrote:

>>> No, we can't leave backslashes unescaped: that's a compatiblity can of 
>>> worms I don't want to open. Consider the result of a $dbh->quote() 
>>> that's stored by the app and then reused - but with a different SCS 
>>> setting!
>
>> That seems like something that Shouldn't Be Done. $dbh->quote() is a 
>> contextual operation anyway that depends on the database handle in 
>> question, and as discussed here, possibly the particular connection. It 
>> seems it should be documented that quote()d strings should not be 
>> stored; strings should be quoted immediately before being used.
>
> Well, I've not heard of anyone actually doing that, but never 
> underestimate the ability of people to misuse the tools they have in 
> strange and interesting ways. To be fair, up until now, the output has 
> been completely consistent across all connections and versions.

Certainly. And I presume few will read upgrade notes ...

But what is the alternative? Escaping a backslash is simply wrong in an 
E''-quoted string, so we have to consider the SCS and non-SCS quote-reuse 
scenario anyway, don't we? I guess you're thinking it should fail safe, 
and I guess it does, but failing with extra \ is pretty ugly and does mess 
up data. I suppose that's when someone can go read the upgrade notes. :)

>> Why not *always* use E'' if the server can handle it? I'd rather see 
>> that consistently applied than only when there's a backslash, so people 
>> aren't scratching their heads about the occasional odd E'' quote (which 
>> many assume is a mistake until they learn about it). It'd be simpler as 
>> well.
>
> I considered this route, and the consistency is a very strong argument. 
> The one counter-argument is that using E only when needed is the way 
> Postgres itself does it, via the internal quote_literal function. Would 
> a large notice in the docs for quote() be enough to dispel the potential 
> head scratching if we made it E-as-needed? The other counter-argument is 
> that E'' is pretty ugly and noisy if not needed, and it won't be 99% of 
> the time. I'm still on the fence, but leaning towards "as needed".

Ok, if Postgres's quote_literal does it that way, it makes sense to follow 
suit.

Thanks,
Jon

-- 
Jon Jensen
End Point Corporation
http://www.endpoint.com/