PHP 5.4.36 Released

pg_last_error

(PHP 4 >= 4.2.0, PHP 5)

pg_last_errorRestituisce l'ultimo messaggio d'errore di una connessione

Descrizione

string pg_last_error ([ resource $connessione ] )

pg_last_error() restituisce l'ultimo messaggio di errore della connessione specificata.

I messaggi di errore possono essere sovrascritti da chiamate a funzioni interne a PostgreSQL(libpq). Quindi questa funzione potrebbe non restituire il messaggio di errore corretto, se piĆ¹ errori si sono verificati in una funzione interna di PostgreSQL.

Utilizzare pg_result_error(), pg_result_status() e pg_connection_status() per una migliore gestione degli errori.

Nota:

Questa funzione si chiamava pg_errormessage().

Vedere anche pg_result_error().

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Tamas Bolner
4 years ago
From a practical view there are two types of error messages when using transactions:

-"Normal" errors: in this case, the application should stop the current process and show an error message to the user.

-Deadlock errors. This shows that the deadlock detection process of PostgreSQL found a circle of dependency, and broke it by rolling back the transaction in one of the processes, which gets this error msg. In this case, the application should not stop, but repeat the transaction.

I found no discrete way to find out which case are we dealing with. This interface doesn't support error codes, so we have to search for patterns in the message text.

Here is an example for PostgreSQL database connection class. It throws a PostgresException on "normal" errors, and DependencyException in the case of a broken deadlock, when we have to repeat the transaction.

postgres.php:
<?php
class PostgresException extends Exception {
    function
__construct($msg) { parent::__construct($msg); }
}

class
DependencyException extends PostgresException {
    function
__construct() { parent::__construct("deadlock"); }
}

class
pg {
    public static
$connection;
   
    private static function
connect() {
       
self::$connection = @pg_connect("dbname=foodb user=foouser password=foopasswd");
        if (
self::$connection === FALSE) {
            throw(new
PostgresException("Can't connect to database server."));
        }
    }
   
    public static function
query($sql) {
        if (!isset(
self::$connection)) {
           
self::connect();
        }
       
       
$result = @pg_query(self::$connection, $sql);
        if (
$result === FALSE) {
           
$error = pg_last_error(self::$connection);
            if (
stripos($error, "deadlock detected") !== false) throw(new DependencyException());
           
            throw(new
PostgresException($error.": ".$sql));
        }
       
       
$out = array();
        while ( (
$d = pg_fetch_assoc($result)) !== FALSE) {
           
$out[] = $d;
        }
       
        return
$out;
    }
}
?>

It should be used in this way:

test.php:
<?php
include("postgres.php");

do {
   
$repeat = false;
    try {
       
pg::query("begin");
       
        ...

       
$result = pg::query("SELECT * FROM public.kitten");

        ...

       
pg::query("commit");
    }
    catch (
DependencyException $e) {
       
pg::query("rollback");
       
$repeat = true;
    }
} while (
$repeat);
?>

The normal errors should be caught at the frontend.

Tamas
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