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Date: Tue, 27 May 2008 15:07:20 +0200
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Subject: Re: [PHP-DEV] Streaming Enabled MySQL Driver for PHP - Google Summer
 of Code 2008 - MySQL
From: uwendel@mysql.com (Ulf Wendel)

Hi!

KishoreKumar Bairi schrieb:
> 1. resource mysqli_get_blob ( mysqli link, string reference )
> 
> reference: is the string which used after database part in the referencing
> URL.
> It can be repository Id (or) "<table>/<column>/<row condition>".

PHP streams are a better choice than PHP strings for handling large 
string objects. PHP strings are loaded into memory at once. For a 
streaming engine you do not want to load large portions of data into 
memory unless you really have to.

Why does this function return a resource? What type of resource is it 
and what is the resource handle used for?

> 
> 2. string mysqli_put_blob ( mysqli link, string file_path, string mode , int
> length )
> 
> file_path: is the path of the file which is to be stored in a blob field.
> 
> mode: mode specifier if the file should be read ASCII mode or binary mode.

PHP strings are binary safe. There are no ASCII mode strings. Why do you 
want to distinguish between ASCII and binary strings? Why is the 
functionality restricted to existing files? Looks a bit like its 
inspired by ftp or Windows?

In general, I think such blob streaming functionality should use PHP 
streams. After some discussion with Andrey I'm not even sure if there is 
a need to introduce a single new API call to ext/mysqli. Andrey brought 
up the idea of using a streams protocol wrapper [1]. This would give you 
quite a neat API which is more powerful and flexible than the above 
suggestion.

Here's an example in pseudo-code.

Reading data from the blob repository:

$stream = fopen('mysqlblob://user:password@socket/db/table/whateverid', 
'r');
while ($chunk = fread($stream, 1024))
   // read blob in 1k chunks
   echo $chunk;
fclose($stream);

Writing data from a file to the blob repository:

$blob_stream = 
fopen('mysqlblob://user:password@host/https=0&id=/db/table/id', 'rw');
$file_stream = fopen('myimage.jpg');
$num_chunks = 0;
while (stream_copy_to_stream($file_stream, $blob_stream, 1024) > 0) {
   printf("Writing to stream... %04dkb\n", $num_chunks++);
}
// the unique id generated by the blob engine to identify the blob
$blob_id = fgets($blob_stream);
fclose($file_stream);
fclose($blob_stream);

Generating data in PHP and writing to the blob repository:

$blob_stream = fopen('mysqlblob://user:password@socket/options', 'w');
// create thumbnail
$image = new Imagick('image.jpg');
$image->thumbnailImage(100, 0);
fwrite($blob_stream, $image);
// get unique blog id from the blob engine
$blob_id = fgets($blob_stream);
fclose($blob_stream);
echo $image;

And, and, and... - streams are a very mighty tool. I'm not sure about 
the syntax for connections. It could be something like this:

URL:
   mysqlblob://user:password@[socket|host]?[param=value[&param=value...]]

Params:
  id       - id of the blob to fetch/read
  port     - MySQL server port
  ssl      - SSL parameter
  ssh      - SSH parameter

Whatever you need.

Ulf


[1] http://www.php.net/manual/en/wrappers.php


-- 
Ulf Wendel, MySQL
Sun Microsystems GmbH,   Sonnenallee 1,   D-85551 Kirchheim-Heimstetten
Geschaeftsfuehrer: Thomas Schroeder, Wolfgang Engels, Dr. Roland Boemer
Vorsitzender des Aufsichtsrates: Martin Haering     Muenchen: HRB161028