Marcel Kornacker did implement concurrency for GiST - I confirmed as much with Joe Hellerstein (his advisor). I know there's a paper he wrote with C.Mohan on it. I don't know which version his implementation was for.
The 7.4 GiST docs have a link to Kornacker's thesis that details how to implement concurrent GiST and unique GiST:
http://citeseer.nj.nec.com/448594.html
I have been reading it, but I think my skills aren't really sufficient to implement it :P
Chris
---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
