Re: [Q] storing JSON, problem with 'escapes'

On Fri, 2008-11-21 at 16:18 -0500, V S P wrote:
> Hi Andrew
>
> that's the thing: when I construct my SQL nowhere do I have
> double-backslashes -- I only have one backslash (generated by
> PHP json_encode to escape the doublequote)

The extra backslashes were there because you had the PHP magic
backslashes option turned on. In my experience that option will do the
wrong thing at some point and almost always ends up being the cause of
strange inserts with additional backslashes in them. I turn it off
everywhere I see it.

Cheers,
Andrew.

> So I never have
> > INSERT INTO blah ( json_column )
> > VALUES ( 'VLADIKVLADIKVLADIKVLADIK(\\"b2122\\")' )
>
> I do see it however when logging SQL statements from within PG. So my
> thought now is that it is PDO that's doing it
> (PDO documentation states that it is doing its own escaping
> for all the drivers)
>
>
> However, I followed your advice and
> set standard_conforming_strings to 'On'
>
> Now, without modifying a single line of my PHP code
> a) the warnings are gone
> b) Postgresql shows only single backslash (which is how I am sending
> it).
>
> So now, I am more confused, as I do not know what was putting
> the second backslash -- may be it was postgresql?
>
> But it works... I think and the behaviour is now how I am expecting it:
> the JSON strings are stored exactly as they are coming out
> of PHP's json_encode (with single backslash in front of a doublequote)
>
>
> thank you
>
>
>
>
>
>
>
>
> On Fri, 21 Nov 2008 23:28:46 +1300, "Andrew McMillan"
> <andrew(at)morphoss(dot)com> said:
> > On Fri, 2008-11-21 at 01:54 -0500, V S P wrote:
> > > Hi,
> > > I am using PHP's json_encode function on
> > > an array of strings
> > > that gives me back a JSON encoded string.
> > >
> > > Some of the elements in the string arrays have
> > > double quotes. So PHP's json_encode correctly
> > > escapes them (according to JSON specifications)
> > > with \.
> > >
> > > For example here is a an array element
> > >
> > > "if( js_iop_lt(a,b) ){ VLADIKVLADIKVLADIKVLADIK("b2122") ;}"
> > >
> > > would get encoded in JSON as
> > >
> > > "if( js_iop_lt(a,b) ){ VLADIKVLADIKVLADIKVLADIK(\"b2122\") ;}"
> > >
> > > And that's correct.
> > > Now, the problem is that with PDO (or may be postgresql itself)
> > > I get
> > >
> > >
> > > "if( js_iop_lt(a,b) ){ VLADIKVLADIKVLADIKVLADIK(\\"b2122\\") ;}"
> > >
> > >
> > > and I get then the POSTGRESQL warning
> > >
> > > WARNING: nonstandard use of \\ in a string literal at character 240
> > > HINT: Use the escape string syntax for backslashes, e.g., E'\\'.
> >
> > When you construct your SQL, if you are going to construct it as a
> > string, like:
> >
> > INSERT INTO blah ( json_column )
> > VALUES ( 'VLADIKVLADIKVLADIKVLADIK(\\"b2122\\")' )
> >
> > You need to instead insert as:
> >
> > INSERT INTO blah ( json_column )
> > VALUES ( E'VLADIKVLADIKVLADIKVLADIK(\\"b2122\\")' )
> >
> >
> > The "E" in front of the string is a special PostgreSQL thing which
> > explains that the string is encoded with \ escaping.
> >
> > See:
> >
> > http://www.postgresql.org/docs/8.3/interactive/sql-syntax-lexical.html
> >
> >
> > particularly the box labelled 'caution' and the paragraph above it.
> >
> > Regards,
> > Andrew McMillan.
> >
> --
> V S P
> toreason(at)fastmail(dot)fm
>
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