I have a table which I'll call table_x holding file attachments as binary large objects in an Oracle database.
However, it does not have one row per file, it has one row per 28kb chunk of a file. Each blob is never more than 28kb.
Rows might look like:
attachsysfilename file_seq file_size file_data
blah.xlsx 0 12000 <BLOB>
poo.xlsx 0 28000 <BLOB>
poo.xlsx 1 9000 <BLOB>
No row has a file size > 28000 bytes. Each attachsysfilename and file_seq combination is unique. When a file is above 28000 bytes, it is split across 2+ rows depending on how many 28kb chunks are needed to store the file.
If I directly export the blobs from the database, I need to concatenate blobs that are stored on 2+ rows before opening them. For example if I had a 2 part Excel file downloaded, I'd have to combine the parts, if using Windows, like type part1.xlsx part2.xlsx > combined.xlsx on the command line. The combined file would open properly, but opening either part individually would return an error.
I am writing some pages in PHP that access this data using PDO and would like to use PHP to similarly concatenate 2+ blobs when they represent the same file.
I have no problem writing a page to download files that are stored on only one row (28kb or less in size). I have that working as follows:
$att = $cono -> prepare (" SELECT attachsysfilename,
file_size,
file_data
from table_x
where attachsysfilename = :file_id
");
$att -> bindParam(':file_id', $file_id, PDO::PARAM_STR);
$att -> execute();
$att -> bindColumn(1, $attachsysfilename, PDO::PARAM_STR, 256);
$att -> bindColumn(2, $file_size, PDO::PARAM_STR, 256);
$att -> bindColumn(3, $file_data, PDO::PARAM_LOB);
$att_row = $att -> fetch( PDO::FETCH_BOUND );
header("Content-type: application/vnd.openxmlfo");
header("Content-Disposition: inline; filename = $attachsysfilename");
fpassthru($file_data);
The above works fine whenever the file is limited to 1 row of the table.
This is my best attempt at handling those files on 2+ rows:
$att = $cono -> prepare (" SELECT attachsysfilename,
file_size,
file_data
from table_x
where attachsysfilename = :file_id
");
$att -> bindParam(':file_id', $file_id, PDO::PARAM_STR);
$att -> execute();
$att -> bindColumn(1, $attachsysfilename, PDO::PARAM_STR, 256);
$att -> bindColumn(2, $file_size, PDO::PARAM_STR, 256);
$att -> bindColumn(3, $file_data, PDO::PARAM_LOB);
$combined_blob = '';
while ( $att_row = $att -> fetch( PDO::FETCH_BOUND ) )
{
$combined_blob = $combined_blob . $file_data;
}
header("Content-type: application/vnd.openxmlfo");
header("Content-Disposition: inline; filename = $attachsysfilename");
fpassthru($combined_blob);
?>
Which returns this error (in the downloaded files):
<b>Warning</b>: fpassthru() expects parameter 1 to be resource, string given in ....
The goal is to combine the 2+ blobs in php so that the combined blob can be downloaded as a file, not any one part.
