Re: FOR SHARE vs FOR UPDATE locks

Simon Riggs wrote:

> ISTM that multitrans could be used here. Two xids, one xmax.

Hmm, yeah, this seems a reasonable suggestion.  The problem is that we
don't have a mechanism today for saying "this Xid holds a shared lock,
this one holds an exclusive lock".  So code-wise it wouldn't be simple
to do.  It's a single bit per Xid, but I don't see where to store such a
thing.

I'm not sure we can use the simple "raise an ERROR" answer though,
because for users that would be a regression.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support