Locking in Postgres

Hello,

I am looking for a database system where it is not too
complicate to integrate some special locking mechanisms
and I am considering Postgres as an candidate.
I have seen that up to now, Postgres uses relation level
locking.
To get a rough estimate of how long the integration of
new locking methods would take and 
how complicate this would be, let's take as example the 
integration of row/page level locking into Postgres.

- which parts of the code would have really to be accessed/changed/modified?
- what would be the time estimate to do so?

Thanks a lot in advance for any answer.

Bettina Kemme

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Bettina Kemme                                
Institute of Information Systems             
ETH Zentrum                 Phone:  +41 1 632 7258
CH-8092 Zuerich             Fax:    +41 1 632 1172
Switzerland                 E-mail: kemme@inf.ethz.ch
http://www.inf.ethz.ch/personal/kemme