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From: Dmitry Igrishin <dmitigr@gmail.com>
Date: Wed, 5 Jan 2022 20:20:36 +0300
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Subject: Re: psycopg3 - parameters cannot be used for DDL commands?
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Les <nagylzs@gmail.com>, pgsql-interfaces@lists.postgresql.org
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=D1=81=D1=80, 5 =D1=8F=D0=BD=D0=B2. 2022 =D0=B3. =D0=B2 20:07, Tom Lane <tg=
l@sss.pgh.pa.us>:
>
> Les <nagylzs@gmail.com> writes:
> > PostgreSQL server log:
>
> > 2022-01-05 17:35:25.831 CET [58] ERROR:  syntax error at or near "$1" a=
t
> > character 35
> > 2022-01-05 17:35:25.831 CET [58] STATEMENT:  ALTER USER postgres WITH
> > PASSWORD $1
>
> Yeah, as a general rule parameters can only be used in DML commands
> (SELECT/INSERT/UPDATE/DELETE).  Utility commands don't support them
> because they don't have expression-evaluation capability.
>
> (Perhaps this will change someday, but don't hold your breath.)
>
> > Passwords can also contain special characters. If I can't use parameter=
s to
> > do this, then how should I quote them in a safe way?
>
> Most client libraries should have a function to convert an arbitrary
> string into a safely-quoted SQL literal that you can embed into the
> command.  I don't know psycopg3, so I don't know what it has for that.
My C++ library, - Pgfe, - can convert any named parameter into an
arbitrary part of SQL expression by using Sql_string::replace()
method. For example:
  update :foo
could be replaced to
  update foo set bar =3D 'baz' where id =3D 1
by using
  s.replace("foo", R"(set bar=3D'baz' where id =3D 1)").