Postgresql SQLSTATE[42P18]: Indeterminate datatype with PDO and CONCAT - postgresql

Question

I'm having issues with CONCAT() when used on a WHERE, in PDO.
The code:
<?php
require_once('config.php');
$fdate = '01/01/2010';
$tdate = '31/12/2030';
$identification = '';
$count = "SELECT count(*) as total FROM ( select time_id from doc_sent WHERE date >= :fdate AND date <= :tdate AND identification LIKE concat('%',:identification,'%') ) x;";
//$count = "SELECT count(*) as total FROM ( select time_id from doc_sent WHERE date >= :fdate AND date <= :tdate ) x;";
$stmt_count_row_main_table = $pdo->prepare($count);
$stmt_count_row_main_table->execute(['fdate' => $fdate, 'tdate' => $tdate, 'identification' => $identification]);
//$stmt_count_row_main_table->execute(['fdate' => $fdate, 'tdate' => $tdate]);
$count_row_main_table = $stmt_count_row_main_table->fetch();
print_r( $count_row_main_table);
?>
The code works when the 'identification' part is commented.
When I'm trying to use CONCAT(), it doesn't.
I tried many "version" of CONCAT() (and read many other questions, like this one: How do I create a PDO parameterized query with a LIKE statement? ) but I am always referring to the main documentation:
https://www.postgresql.org/docs/9.1/static/functions-string.html
Which say:
concat('abcde', 2, NULL, 22) --> abcde222
The FULL error when I use CONCAT() is:
PHP Fatal error: Uncaught PDOException: SQLSTATE[42P18]: Indeterminate datatype: 7 ERROR: could not determine data type of parameter $3 in /var/www/pdo-reporter/show.php:17\nStack trace:\n#0 /var/www/pdo-reporter/show.php(17): PDOStatement->execute(Array)\n#1 {main}\n thrown in /var/www/pdo-reporter/show.php on line 17
What's wrong with my code?

Answer 1

CONCAT is a function that takes a VARIADIC argument list, which means that internally postgres will convert them into an array of the same type.
postgres=# \df concat
List of functions
Schema | Name | Result data type | Argument data types | Type
------------+--------+------------------+---------------------+------
pg_catalog | concat | text | VARIADIC "any" | func
When trying to resolve the input type to a single type, the SQL parser fails. It can be reproduced in this simpler form:
postgres=# PREPARE p AS select concat('A', $1);
ERROR: could not determine data type of parameter $1
The parser can't figure out the datatype of $1 so it errs on the side of caution.
One easy solution is to cast the parameter as text:
postgres=# PREPARE p AS select concat($1::text);
PREPARE
or with the CAST operator:
postgres=# PREPARE p AS select concat(cast($1 as text));
PREPARE
I haven't tested with PDO but presumably it would work (given how it deals with parameters to produce prepared statements) to change the query to:
"...identification LIKE '%' || :identification || '::text%'..."
or use the '||' operator instead of concat in the query:
identification LIKE '%' || :identification || '%'
EDIT: BTW if you want to find that a parameter :X is a substring of identification, this clause is more secure: strpos(identification, :X) > 0, because :X may contain '%' or '_' without causing any side-effect in the match, contrary to what happens with LIKE.