info about patch: using parametrised query in psql

Hello

I try to explain my motivation for creating this patch
https://commitfest.postgresql.org/action/patch_view?id=224 .

Parametrised queries are supported in PostgreSQL long time. Using the
parametrised queries is point of all advices about good programming
style. On application level it is protection to SQL injection. On low
level it is protection to some potential quoting or escaping bugs. It
is paradox, so PostgreSQL doesn't use this techniques in own
applications - mainly in psql.

In psql we have not any quoting, or escaping functionality. We have to
use external tools like awk, sed:

http://www.redhat.com/docs/manuals/database/RHDB-2.1-Manual/admin_user/r1-app-psql-4.html

>
> testdb=> \set content '\'' `cat my_file.txt` '\''
> testdb=> INSERT INTO my_table VALUES (:content);
>
> One possible problem with this approach is that my_file.txt might contain single quotes.
> These need to be escaped so that they do not cause a syntax error when the
> third line is processed. You can do this with the program sed:
>
> testdb=> \set content `sed -e "s/'/\\\\\\'/g" < my_file.txt`

Similar problems could be removed with using parameter queries in psql.

With this parametrised queries feature you can:

\set content `cat my_file.txt`
INSERT INTO my_table VALUES(:content);

and this command will be correct without depending on content my_file.txt file.

This is more: robust, secure, and simpler.

My motivation is simplify life to people who use psql for scripting.
For internal use SQL injection isn't too much terrible. Problem are
some obscure identifiers used some users. Now you have to carefully
check every value, if your scripts have to be robust.

Patch doesn't change default behave. You have to explicitly activate it.

Regards,
merry Christmas

Pavel Stehule