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Re: Compressing data in a lob column in Oracle9i

From: Peter Sylvester <>
Date: Thu, 29 Apr 2004 13:16:51 -0400
Message-ID: <c6rda3$sp1$>

I'm not sure, but I seem to recall reading about some issues when trying to manipulate LOBs through triggers. You should probably check into this before you spend much time trying to implement your own compression scheme.


Prem K Mehrotra wrote:
> I had read about the compression feature added in Oracle9i, i.e., a
> table can be compressed. However, when I found an application to use
> compression, I was terribly disappointed that Oracle compression does
> not work on LOB data types.
> Basically I have a packaged application (code supplied by third
> party). There is a table which contains blob column and I want to
> compress this column. Since it is a packaged appalication, all I can
> do is to add triggers if they do not cause side effects.
> I was thinking of adding a trigger on insert/update which will
> compress the data stored in LOB column. Will it work? My question is -
> are there any functions available in PL/SQL for compressing a
> character string. Also I don't know when LOB data is stored in
> database (using OCI - I know packaged application uses OCI), does all
> lob data in a blob come as a unit in a trigger (even though OCI may
> send it in parts).
> If I am not mistaken, Oracle 9i provides triggers on select (FGA). I
> presume I can uncompress the LOB data inside select trigger. Once
> again, is there a function avaiable in
> PL/SQL for uncompressing. I have never used select trigger only read
> about them.
> IF there is no function for compress/uncompress in PL/SQL are there
> functions avaiable in Java since Java can be used in triggers.
> Thansk a lot,
> Prem
Received on Thu Apr 29 2004 - 12:16:51 CDT

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