First of all you can set LongReadLen to the bigest size a BLOB will except
and it will only fetch the right amount.
In your case, it's probably best to use blob_read method to fetch in chunks.
See Readme.longs in DBD::Oracle package for examples.
Ilya
-----Original Message-----
From: Adam Kennedy
To: [EMAIL PROTECTED]
Sent: 9/20/01 8:30 PM
Subject: Large BLOBs
Hi there
I'm trying to find a mechanism for dealing with large BLOBs, where large
is
a value greater than the memory available to the process.
This is used in a CGI application.
I've been reading through and docs and source to DBI and DBD::Oracle.
I've
checked pretty much every resource I can find, and everything so far has
either said
1. Set LongReadLen to a bigger value.
This won't help because I can't set LongReadLen large enough
obviously...
BTW, I do know what the size of the BLOBs are, using a
SELECT DBMS_LOB.GETLENGTH($field) AS $field FROM $table
type command. The largest BLOB I'm currently dealing with is 50meg.
While
the server ( E10000 ) has the memory to deal with this, the sysadmins
had a
fit when I told them about having to use 50-60 meg of ram for the
process,
especially since I have the added burden of not being able to write to
the
filesystem ( ipsec policies ), so I can't just read from the database
and
dump to the filesystem, free up the memory, and then stream to the
browser.
I have to stream the file direct from the database to the browser, so
that
50meg process might be running for half an hour or so... ( or longer
depending on browser bandwidth ). I expect te concurrency level to be
fairly
low, so running 5 or 10 smaller processes would be acceptable.
2. "BLOBs are hard and database dependant"
This is obvious, however I would have thought that there would be a way
of
doing this.
Possible Solutions
IO::BLOB::Pg is a nice little module for PostgreSQL that let's you treat
a
BLOB in the database as a filehandle, and from there I imagine a
bufferred
read/write to the browser ( STDOUT ) would be a piece of cake. Something
similar to this would be very handy. I'm on the verge of giving up and
trying to write something like IO::BLOB::Oracle, but I'd like to exhaust
any
possible alternatives first.
Of course, there could be something I'm missing...
Oh, one more thing. DBD::Oracle does the downloading of the BLOB for you
when you select it's field... is there a way to override this, and JUST
get
the BLOB identifier?
Thanks
Adam
