UPSERT

Hello,

I'd like to work on TODO item:
> Add REPLACE or UPSERT command that does UPDATE, or on failure, INSERT

could you please tell me if I'm going in the right way?

There are some different syntaxes possible, but MySQL has an interesting
one here:
http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html

INSERT INTO table (a,b,c) VALUES (1,2,3) ON DUPLICATE KEY UPDATE c=c+1;
This allow to make an insert, and if the key is already there to modify
the value depending on the current one.

Then I have two choices possible:
- Search for existing tuples among key or unique constraint, then if
nothing is found, insert it.
- Try to insert a new row, catch if there is any error, and then search
for all tuple matching.

As it would be a new command, I have no idea on what the data could be.
Does syntax meet your needs? Which choice should I implement?

Regards
Jonathan Scher