Thread: BUG #2629: libpq - Cannot deallocate prepared statement created with PQprepare()

The following bug has been logged online:

Bug reference:      2629
Logged by:          Andy McCurdy
Email address:      andy.mccurdy@emergent.net
PostgreSQL version: 8.1.4
Operating system:   Windows XP
Description:        libpq - Cannot deallocate prepared statement created
with PQprepare()
Details:

According to http://www.postgresql.org/docs/8.1/interactive/libpq-exec.html,
the last statement in the PQprepare() function description suggests that a
user can run the statement: "DEALLOCATE [statement name]" with PQexec() to
deallocate a statement prepared with PQprepare().  When trying to do this, I
consistently get the error message:

ERROR:  prepared statement "[statement name]" does not exist

Here's a snippet of code that illustrates what I am attempting to do:

int main()
{

PGconn* conn;
PGresult* result;

conn = PQsetdbLogin("localhost", "5432", NULL, NULL, "postgres", "postgres",
"postgres");

result = PQprepare(conn, "MyQuery", "select * from pg_stat_activity", 0,
NULL);

/*
THE FOLLOW PQEXEC() FAILS.  Error message says:  ERROR:  prepared statement
"myquery" does not exist"
*/
result = PQexec(conn, "DEALLOCATE MyQuery");


result = PQexec(conn, "PREPARE MyQuery AS select * from pg_stat_activity");

/*
THIS WORKS
*/
result = PQexec(conn, "DEALLOCATE MyQuery");



return 0;
}

On Fri, Sep 15, 2006 at 07:39:32AM +0000, Andy McCurdy wrote:
> result = PQprepare(conn, "MyQuery", "select * from pg_stat_activity", 0,
> NULL);
>
> /*
> THE FOLLOW PQEXEC() FAILS.  Error message says:  ERROR:  prepared statement
> "myquery" does not exist"
> */
> result = PQexec(conn, "DEALLOCATE MyQuery");

You prepared a mixed-case identifier so you'll need to quote it in
SQL statements to preserve its case.  Unquoted identifiers are
folded to lowercase, as the error message shows.

result = PQexec(conn, "DEALLOCATE \"MyQuery\"");

See "Identifiers and Key Words" in the "SQL Syntax" chapter of the
documentation for more information about quoted identifiers.

http://www.postgresql.org/docs/8.1/interactive/sql-syntax.html#SQL-SYNTAX-IDENTIFIERS

--
Michael Fuhr

"Andy McCurdy" <andy.mccurdy@emergent.net> writes:
> result = PQprepare(conn, "MyQuery", "select * from pg_stat_activity", 0,
> NULL);

I believe the above will result in preparing a statement named "MyQuery",
ie, no case-folding happens on the second argument of PQprepare, because
it never goes through the SQL parser.

> /*
> THE FOLLOW PQEXEC() FAILS.  Error message says:  ERROR:  prepared statement
> "myquery" does not exist"
> */
> result = PQexec(conn, "DEALLOCATE MyQuery");

I think this would work:

result = PQexec(conn, "DEALLOCATE \"MyQuery\"");

            regards, tom lane