Обсуждение: Request for builtin function: Double_quote

Folks,

Given the amount of qoute nesting we do in Postgres, I thought that we need a
function that handles automatic doubling of quotes within strings.   I've
written one in PL/pgSQL (below).  I'd really love to see this turned into a
builtin C function.

-Josh

CREATE FUNCTION double_quote(text) returns text as '
DECLARE bad_string ALIAS for $1;       good_string text;       current_pos INT;       old_pos INT;
BEGIN       IF bad_string IS NULL or bad_string = '''' THEN               RETURN bad_string;       END IF;
good_string:= bad_string;       current_pos :=  STRPOS(good_string, chr(39));       WHILE current_pos > 0 LOOP
    old_pos := current_pos;               good_string := SUBSTR(good_string, 1, (current_pos - 1)) ||
   repeat(chr(39), 2) || SUBSTR(good_string, (current_pos  
+ 1));               current_pos := STRPOS(SUBSTR(good_string, (old_pos + 2)),
chr(39));               IF current_pos > 0 THEN                       current_pos := current_pos + old_pos + 1;
     END IF;       END LOOP; 
RETURN good_string;
END;'
LANGUAGE 'plpgsql'
WITH (ISCACHABLE, ISSTRICT);

Josh, 
I'm not sure what you mean by 'builtin C function'. 
There is one already size_t PQescapeString (char *to, const char *from, size_t length); 
Or do you mean a String Function like substring(string [from integer] [for integer]) 
I would rather call it 'builtin sql function'. 

Regards, Christoph 

> 
> Folks,
> 
> Given the amount of qoute nesting we do in Postgres, I thought that we need a
> function that handles automatic doubling of quotes within strings.   I've 
> written one in PL/pgSQL (below).  I'd really love to see this turned into a 
> builtin C function.
> 
> -Josh
> 

Josh Berkus <josh@agliodbs.com> writes:
> Given the amount of qoute nesting we do in Postgres, I thought that we need a 
> function that handles automatic doubling of quotes within strings.   I've 
> written one in PL/pgSQL (below).  I'd really love to see this turned into a 
> builtin C function.

What does this do that isn't already done by quote_literal?
        regards, tom lane

Chris, Tom:

Yes, thank you Chris, I meant a builtin SQL function.

> > Given the amount of qoute nesting we do in Postgres, I thought that
> we need a 
> > function that handles automatic doubling of quotes within strings.
>   I've 
> > written one in PL/pgSQL (below).  I'd really love to see this
> turned into a 
> > builtin C function.
> 
> What does this do that isn't already done by quote_literal?

Well, first off, quote_literal isn't in the documentation under
"Functions and Operators".    So this is the first I've heard about it
-- or probably anyone else outside the core team.   How long has it
been around?

Second, double_quote does not return the outside quotes, just the
inside ones ... it's for passing string values to EXECUTE statements. However, now that I know that quote_literal
exists,I can simplify
 
the double_quote statement considerably.  

Therefore, I withdraw my initial request, and request instead that
quote_literal be added to the function documentation in String
Functions and Operators.

I will event supply text for the functions table:

function            returns        
quote_literal(string text)    text        

explain
Returns the entire string passed to it, including quote marks.  Useful
for nesting quotes, such as in the EXECUTEing dynamic queries.

example            result
quote_literal('O''Reilly')    'O''Reilly'


-Josh Berkus

-Josh Berkus

"Josh Berkus" <josh@agliodbs.com> writes:
> Well, first off, quote_literal isn't in the documentation under
> "Functions and Operators".    So this is the first I've heard about it
> -- or probably anyone else outside the core team.   How long has it
> been around?

Awhile; however, the only documentation was in the discussion of EXECUTE
in the pl/pgsql chapter of the Programmer's Guide, which is probably not
the best place.

> Therefore, I withdraw my initial request, and request instead that
> quote_literal be added to the function documentation in String
> Functions and Operators.

Done; I also added its sister function quote_ident.  See the devel
docs at
http://candle.pha.pa.us/main/writings/pgsql/sgml/functions-string.html
        regards, tom lane

Tom,

> Done; I also added its sister function quote_ident.  See the devel
> docs at
> http://candle.pha.pa.us/main/writings/pgsql/sgml/functions-string.html

Tante Grazie.

--
-Josh Berkus