Обсуждение: show value of backslashes in string array argument

Hi there,

I have a problem using backslash character as part of a string array item.

I use "PostgreSQL 8.2.4 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC) 
3.4.2 (mingw-special)" version, with standard_conforming_strings = 'on'.

I found that, is that in spite of using standard_conforming_strings = 'on', 
the string array items are shown in C escape sequences conventions.

Use the following scenario:   - create a table with       CREATE TABLE test       (         "colVarchar" character
varying,        "colVarcharArray" character varying[]       )   - insert a row with a string composed by just one
characterbackslash, 
 
and an array with just one item, with the same value of one backslash, with:       INSERT INTO test VALUES ( '\',
ARRAY['\' ] );   - show the values with:       SELECT * FROM test
 

And the result is:
colVarchar | colVarcharArray
------------+-----------------\          | {"\\"}

The question is why the two strings are shown different in spite they are 
the same, and standard_conforming_strings = 'on' ?

Sabin

If you do 
SELECT "colVarchar","colVarcharArray"[1] FROM test;
you will see that you get identical values.


-- 
Achilleas Mantzios 

I fond another collateral problem, because there are the different 
convention to describe a varchar array item which contains backslashes, when 
standard_conforming_strings = 'on'

For instance, to get a string composed by just one character backslash I can 
use any of the two forms:
   SELECT ARRAY[ '\' ]::varchar[];

or
   SELECT '{\\}'::varchar[];

On the other hand, standard_conforming_strings = 'on' let me use varchar 
items with '\' format. So the first format seems to be aware of 
standard_conforming_strings = 'on', but the second is not.

My problem is that the java driver build arrays using the second format, but 
the driver seems to be aware of standard_conforming_strings = 'on'. This 
make inconsistence using the statement parameters, because to get the same 
thing in the database I have to initialize a varchar parameter with a string 
of one backslashes, but a varchar array item has to be initialized with a 
string of two backslashes.

Sabin 

Στις Δευτέρα 12 Νοέμβριος 2007 11:51, ο/η Sabin Coanda έγραψε:
> I fond another collateral problem, because there are the different
> convention to describe a varchar array item which contains backslashes,
> when standard_conforming_strings = 'on'
>
> For instance, to get a string composed by just one character backslash I
> can use any of the two forms:
>
>     SELECT ARRAY[ '\' ]::varchar[];
>
> or
>
>     SELECT '{\\}'::varchar[];
>
> On the other hand, standard_conforming_strings = 'on' let me use varchar
> items with '\' format. So the first format seems to be aware of
> standard_conforming_strings = 'on', but the second is not.
>
> My problem is that the java driver build arrays using the second format,
> but the driver seems to be aware of standard_conforming_strings = 'on'.
> This make inconsistence using the statement parameters, because to get the
> same thing in the database I have to initialize a varchar parameter with a
> string of one backslashes, but a varchar array item has to be initialized
> with a string of two backslashes.
>
> Sabin

I would recommend:

a) Move to Unix
b) Subscribe to pgsql-jdbc@postgresql.org

>
>
>
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--
Achilleas Mantzios

"Sabin Coanda" <sabin.coanda@deuromedia.ro> writes:
> I found that, is that in spite of using standard_conforming_strings = 'on', 
> the string array items are shown in C escape sequences conventions.

That's how it's supposed to be.  See
http://www.postgresql.org/docs/8.2/static/arrays.html#AEN5876
        regards, tom lane

"Tom Lane" <tgl@sss.pgh.pa.us> wrote in message 
news:6268.1194883527@sss.pgh.pa.us...
> That's how it's supposed to be.  See
> http://www.postgresql.org/docs/8.2/static/arrays.html#AEN5876

Hi Tom,

I read it and I understood there are 2 cascaded parsers, but I didn't find 
an explicit reference to the behavior related to 
standard_conforming_strings.

But after some tests, I found the following behaviors:
- the 1st parser is the SQL interpreter which is aware of 
standard_conforming_strings (on or off)
- the 2nd parser which is an array interpreter, doesn't care of 
standard_conforming_strings, using every time C escape conventions

Please confirm me whether I understand it correctly or not.

TIA,
Sabin