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Serving Large Data From Files or From Blobs

 
 
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      02-15-2008
My question is partly a language issue (memory) and partly a Web issue
(where the program runs), so I hope everyone will be open to helping.

Users may submit and store pictures with my program. I have the choice
of storing these pictures either as files on the server or as a blob
in the database. The pictures are just user data, and it seems logical
to keep them in the database with all the other data. But I'm
concerned about how to serve these pictures. I can write a program to
handle image requests and return the appropriate picture from the
database. But it seems to me this means the picture will need to be
read from the database and stored in memory, in a variable, then
written from the variable to the HTTP response.

The part where the whole picture is stored in a variable is the part
that worries me. Is this impractical? Or merely a bad idea? Is storing
the pictures as files, allowing the server to serve them as it would
server anything else, the best option?
 
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xhoster@gmail.com
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      02-15-2008
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
> My question is partly a language issue (memory) and partly a Web issue
> (where the program runs), so I hope everyone will be open to helping.
>
> Users may submit and store pictures with my program. I have the choice
> of storing these pictures either as files on the server or as a blob
> in the database. The pictures are just user data, and it seems logical
> to keep them in the database with all the other data. But I'm
> concerned about how to serve these pictures. I can write a program to
> handle image requests and return the appropriate picture from the
> database. But it seems to me this means the picture will need to be
> read from the database and stored in memory, in a variable, then
> written from the variable to the HTTP response.


Databases that support blob types generally support ways to either stream
those blobs or efficiently read them in chunks. How to do that would
depend on the specifics of the database being used.

How are you getting the data into the database in the first place without
having it all in memory at once?

> The part where the whole picture is stored in a variable is the part
> that worries me. Is this impractical?


It depends on the maximum practical size of the image, and the amount of
memory your server has. Only you can know those things.


> Or merely a bad idea? Is storing
> the pictures as files, allowing the server to serve them as it would
> server anything else, the best option?


Do the file contents need the same transactional behavior (ACID, etc.)
as the rest of the stuff in database?

Xho

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Rik Wasmus
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      02-15-2008
On Fri, 15 Feb 2008 18:44:50 +0100, <(E-Mail Removed)> wrote:

> My question is partly a language issue (memory) and partly a Web issue
> (where the program runs), so I hope everyone will be open to helping.
>
> Users may submit and store pictures with my program. I have the choice
> of storing these pictures either as files on the server or as a blob
> in the database. The pictures are just user data, and it seems logical
> to keep them in the database with all the other data. But I'm
> concerned about how to serve these pictures. I can write a program to
> handle image requests and return the appropriate picture from the
> database. But it seems to me this means the picture will need to be
> read from the database and stored in memory, in a variable, then
> written from the variable to the HTTP response.
>
> The part where the whole picture is stored in a variable is the part
> that worries me. Is this impractical? Or merely a bad idea? Is storing
> the pictures as files, allowing the server to serve them as it would
> server anything else, the best option?



Insertion & retrieving is very much streamlined (huhu, pun not intended,
but it indeed uses streams) with PDO, look at the Large Objects (LOB)
example at <http://nl.php.net/pdo>:

Insertion:
<?php
$db = new PDO();//put your connections variables here
$stmt = $db->prepare("INSERT INTO tablename (image) values (?)");
$fp = fopen($_FILES['file']['tmp_name'], 'rb');
$stmt->bindParam(1, $fp, PDO:ARAM_LOB);
$stmt->execute();
fclose($fp);
?>

Retrieval:
<?php
$db = new PDO();//put your connections variables here
$stmt = $db->prepare("SELECT image FROM tablename WHERE id = ?");
$stmt->bindParam(1,$_GET['id'],PDO:ARAM_INT);
$stmt->execute();
$stmt->bindColumn(1, $lob, PDO:ARAM_LOB);
$stmt->fetch(PDO::FETCH_BOUND);
header("Content-Type: image/png");//or other format...
fpassthru($lob);
?>
--
Rik Wasmus
 
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