Re: How to indicate end of clob from pl/sql?

On Sep 15, 9:31 am, bclar..._at_gmail.com wrote:
> *snip* post
>
> Thanks to those who responded.
>
> It turns out that I was, in fact, getting eof, but that further on
> downstream the data was blocking waiting for an eof that *I* wasn't
> sending because I didn't close the stream ( though I did flush it ).
>
> Sorry.  But my debugging spidey-sense was kinda drawn to the CLOB
> stuff because they are 'weird' and I don't fully understand them.
>
> I really wish there were a nice simple type like postgres's TEXT type
> in oracle.  I've never had a need for larger than 2 gigs but I have
> had need of larger than 4000 characters on more than one occasion.
>
> Gees...
>
> I believe there is some behind the scenes magic whereby a clob can be
> written to by one thread of execution and read by another at the same
> time so that the reader will block until there more data has been
> written.  This would make a clob like a stream?   I've never had a
> need for this, but the fact that it is ( probably ) there, complicates
> the clob documentation.  Also there is something called chunks.  I
> have not messed with the chunksize either.
>
> Is there a limit to how much of a clob Oracle will buffer?  Say I read
> a whole clob and it happened to be a 3 gigger.  Does that mean the
> clob is stored in memory occupying 3 gigs?  If not, then what if I
> want to read it again?  I hope it is stored where I can get it again
> and not just one chunks worth or something annoyingly complicated like
> that.  Then *I* would be responsible for generating the data again.
> Sheesh!
>
> Something simple for bears-of-little-brain would be nice...
>
> And if there is a way to make such a type using clobs underneath, I
> would need to understand 'how it works' enough to trust 'that it
> works'.  For that I would need to understand clobs enough to write it
> myself, and then the benefit of it would be somewhat diminished.
> Oracle really ought to supply it documenting any performance
> limitations.
>
> And LONG doesn't work.  It's deprecated.

You post reads like you are just complaigning because you do not understand how to properly deal with CLOBs. The Oracle LOB data types work fine. To understand how the feature works read the Application Developers Guide - Large Objects. In other words there is an entire manual on the subject of LOBs though only a portion of the manual is on CLOB. You can skip over the BLOD and BFILE portions if you only need to understand working with CLOBs. But there is no substitute for the knowledge contained in the manual. It will be beneficial to you to cover this material prior to designing and coding your application.

LOB IO bypasses the buffer cache. The basic unit for LOB operations is the chuck size. When the actual length of the data is large setting the chunk size up may be a reasonable decision.

HTH -- Mark D Powell -- Received on Mon Sep 15 2008 - 09:58:50 CDT