LO to text conversion

Hi all.

I need to store XML documents in database, so I use large objects for
them. Now I have a problem: I want to search for patterns in documents,
and it looks like there is no standard way to do it, so I write
C function to do it, but it has limitation: it is not support regular
expressions. Although it will be easy to use some library to handel
them, but I know that PostgreSQL already has it.

So, my question is: is there any function to search in lobjs? Another
thing which would be enought is convertion of lo to text.

BTW: Somebody can say, that I could use text field for documents as
well, but it is inefficient to embed document in sql query and then
extract it back

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Regards,
ASK