Text and Image Data Handling

The Adaptive Server Enterprise database driver for Perl supports image and a text type for LONG/BLOB data. Each type can as much as 2GB of binary data.

The default size limit for text/image data is 32KB. Use the LongReadLen attribute to change this limit, which is set by a call to the fetch() API.

You cannot use bind parameters to insert text or image data.

When using regular SQL, image data is normally converted to a hex string, but you can use the syb_binary_images handle attribute to change this behavior. As an alternative, you can use a Perl function similar to $binary = pack("H*", $hex_string); to perform the conversion.

As the DBI has no API support for handling BLOB style (text/image) types, the SybaseASE.pm file includes a set of functions you can install, and use in application-level Perl code to call the Open Client ct_get_data() style calls. The syb_ct_get_data() and syb_ct_send_data() calls are wrappers to the Open Client functions that transfer text and image data to and from Adaptive Server.

Example

$sth->syb_ct_get_data($col, $dataref, $numbytes);

You can use the syb_ct_get_data() call to fetch the image/text data in raw format, either in one piece or in chunks. To enable this call, set the dbh->{syb_no_bind_blob} statement handle to 1.

The syb_ct_get_data() call takes these arguments: the column number (starting at 1) of the query, a scalar reference, and a byte count. A byte count of 0 reads as many bytes as possible. The image/text column must be last in the select list for this call to work.

The call sequence is:

$sth = $dbh->prepare("select id, img from a_table where id = 1");
	$sth->{syb_no_bind_blob} = 1;
	$sth->execute;
	while($d = $sth->fetchrow_arrayref) {
		# The data is in the second column
		$len = $sth->syb_ct_get_data(2, \$img, 0);
}

syb_ct_get_data() returns the number of bytes that were fetched, if you are fetching chunks of data, you can use:

while(1) {
$len = $sth->syb_ct_get_data(2, $imgchunk, 1024);
... do something with the $imgchunk ...
 last if $len != 1024;
}