PHP 5.5.15 is released

pg_last_error

(PHP 4 >= 4.2.0, PHP 5)

pg_last_errorRetorna a string da última mensagem de erro de uma conexão

Descrição

string pg_last_error ( resource $connection )

pg_last_error() retorna a última mensagem de erro para a conexão representada por connection.

As mensagens de erro podem ser sobrescritas por chamadas internas ao PostgreSQL(libpq). Se múltiplos erros ocorrerem dentro de um módulo de função do PostgreSQL, pode não retornar a mensagem de erro correta.

Use pg_result_error(), pg_result_status() e pg_connection_status() para um melhor tratamento de erros.

Nota:

Esta função era chamada pg_errormessage().

Veja também pg_result_error().

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Tamas Bolner
3 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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