PostgreSQL prepared statement does not work

Question

When I enter the following prepared statement:

PREPARE pstmt AS SELECT substring(indhold from $1 for $2) FROM mediefil WHERE id = $3

And execute it by entering the following command:

EXECUTE pstmt (1, 524288, '{01428c12-6c7c-148b-ca35-9d344dfbf8e8}')

I get a strange error:

2013-11-25 18:47:37 CET ERROR:  invalid escape string
2013-11-25 18:47:37 CET HINT:  Escape string must be empty or one character.
2013-11-25 18:47:37 CET CONTEXT:  SQL function "substring" statement 1
2013-11-25 18:47:37 CET STATEMENT:  EXECUTE pstmt (1, 524288, '{01428c12-6c7c-148b-ca35-9d344dfbf8e8}')

Why does this happen? And how can I make the prepared statement work?

Answer 1

Try casting the parameters:

PREPARE pstmt(int, int, uuid) AS
SELECT substring(indhold from $1 for $2) FROM mediefil WHERE id = $3