mysqlnd: Fractional seconds truncated in prepared statements, if value of decimals is AUTO_SEC_PART_DIGITS (=39).

Description

This issue was initially reported for MariaDB Connector/C (which uses part of mysqlnd):

In some cases both MySQL and MariaDB server will send the value 39 (=AUTO_SEC_PART_DIGITS) for datetime and time decimals. The binary protocol implementation however will only set fractional seconds if decimals is <= 6.

The following code:

<?php

$link= mysqli_connect("localhost", "georg", null, "test", 0, "/tmp/mysql.sock");

$stmt = $link->prepare("select FROM_UNIXTIME('1992.1'), FROM_UNIXTIME('1992.0')");
$stmt->execute();
$stmt->bind_result($binval[0],$binval[1]);
$stmt->fetch();
$stmt->close();

$result = $link->query("select FROM_UNIXTIME('1992.1'), FROM_UNIXTIME('1992.0')");
$txtval = $result->fetch_row();
$result->close();
$err_cnt= 0;

for ($i=0; $i < 2; $i++)
    if ($txtval[$i] != $binval[$i])
        printf("[%03d] Expected '%s' (text protocol), got '%s' (binary protocol)\n",
               $err_cnt++, $txtval[$i], $binval[$i]);

printf("Done!\n");
?>

Resulted in this output:

[000] Expected '1970-01-01 01:33:12.100000' (text protocol), got '1970-01-01 01:33:12' (binary protocol)
Done!

But I expected this output instead:

Done!

Metadata sent by server:

$> mariadb --column-type-info -e"select from_unixtime('1922.1')"
Field   1:  `from_unixtime('1922.1')`
Org_field:  ``
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       DATETIME
Collation:  binary (63)
Length:     26
Max_length: 26
Decimals:   39
Flags:      BINARY 

PHP Version

PHP 8.4.0-dev

Operating System

No response

Commencez par le traitement du protocole binaire de mysqlnd pour les métadonnées DATETIME et TIME, en utilisant la reproduction fournie de la requête préparée mysqli et sa comparaison avec le protocole texte. Vérifiez le cas où le serveur signale les décimales comme 39 (AUTO_SEC_PART_DIGITS), puis ajoutez ou mettez à jour la couverture de régression afin que les secondes fractionnaires soient conservées et que la comparaison affiche « Done! ». از