FETCH_LAZY not properly supported for "long" columns

[cmb69]

Description

The following code:

<?php
const SIZE = 300;
$pdo = new PDO(DSN, USER, PASS);
$pdo->exec("CREATE TABLE gh9498 (name VARCHAR(" . SIZE . "))");
$pdo->exec("INSERT INTO gh9498 VALUES ('" . str_repeat("a", SIZE) . "')");
$statement = $pdo->prepare("SELECT * FROM gh9498");
$statement->execute();
$row = $statement->fetch(PDO::FETCH_LAZY);
var_dump($row);
var_dump($row);

Resulted in this output:

object(PDORow)#3 (2) {
  ["queryString"]=>
  string(20) "SELECT * FROM gh9498"
  ["name"]=>
  string(300) "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
}
object(PDORow)#3 (2) {
  ["queryString"]=>
  string(20) "SELECT * FROM gh9498"
  ["name"]=>
  NULL
}

But I expected this output instead:

object(PDORow)#3 (2) {
  ["queryString"]=>
  string(20) "SELECT * FROM gh9498"
  ["name"]=>
  string(300) "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
}
object(PDORow)#3 (2) {
  ["queryString"]=>
  string(20) "SELECT * FROM gh9498"
  ["name"]=>
  string(300) "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
}

Obviously, accessing the row for the first time works as expected, but accessing it another time, does not. If SIZE < 256, accessing the row multiple times is properly supported.

PHP Version

PHP-8.0

Operating System

any

[cmb69]

Well, it's actually worse, depending on the driver's capabilities. Consider:

$pdo = new PDO(DSN, USER, PASS);
$pdo->exec("DROP TABLE gh9498");
$pdo->exec("CREATE TABLE gh9498 (name1 VARCHAR(256), name2 VARCHAR(256))");
$pdo->exec("INSERT INTO gh9498 VALUES ('" . str_repeat("a", 256) . "', '" . str_repeat("b", 256) . "')");
$statement = $pdo->prepare("SELECT * FROM gh9498");
$statement->execute();
$row = $statement->fetch(PDO::FETCH_LAZY);
var_dump($row->name1);
var_dump($row->name2);

This works as expected, but if we swap the last two rows, the second var_dump() yields NULL for drivers not supporting SQL_GD_ANY_ORDER.

The problem is that "long" columns are not bound, but rather their contents are retrieved using SQLGetData(), and most drivers only support retrieving data this way sequentially (column by column). So if there are multiple "long" columns, retrieving out of order will not work. But, still worse, all columns after a "long" column are automatically treated as "long" columns (required for drivers not supporting SQL_GD_ANY_COLUMN), so even "regular" columns may not properly work with FETCH_LAZY, e.g.

$pdo = new PDO(DSN, USER, PASS);
$pdo->exec("DROP TABLE gh9498");
$pdo->exec("CREATE TABLE gh9498 (name1 VARCHAR(256), name2 VARCHAR(10), name3 VARCHAR(10))");
$pdo->exec("INSERT INTO gh9498 VALUES ('" . str_repeat("a", 256) . "', '" . str_repeat("b", 10) . "', '" . str_repeat("c", 10) . "')");
$statement = $pdo->prepare("SELECT * FROM gh9498");
$statement->execute();
$row = $statement->fetch(PDO::FETCH_LAZY);
var_dump($row->name3);
var_dump($row->name2);

This will fail to retrieve name2.

To fix this, we would need to buffer the column results internally, what would defeat the purpose of LAZY_FETCH. So WONTFIX (and document) appears to be appropriate, but that would likely rule out a potential fix for #9498, which would use SQLGetData() for all columns.

Thoughts?