Excerpts from Florian Pflug's message of vie nov 26 10:48:39 -0300 2010: > On Nov25, 2010, at 23:01 , Alvaro Herrera wrote: > > So I've been working on improving locks for foreign key checks, as > > discussed in a thread started by Joel Jacobson a while ago. I've posted > > about this: > > http://www.commandprompt.com/blogs/alvaro_herrera/2010/11/fixing_foreign_key_deadlocks/ > > http://www.commandprompt.com/blogs/alvaro_herrera/2010/11/fixing_foreign_key_deadlocks_part_2/ > > To me, the whole thing seems to be special case of allowing to not only lock > whole tuples FOR UPDATE or FOR SHARE, but also individual fields or sets of > fields. Except that for simplicity, only two sets are supported, which are > A) All fields > B) All fields which are included in some unique constraint, including > primary keys. > > I'd therefore suggest to extend the FOR SHARE / FOR UPDATE syntax to be > SELECT FOR { SHARE | UPDATE } [ OF <table1>[.<field1>], ... ] > and obtain what you call a "KEY LOCK" if (for a particular table) the set of > fields is a subset of (B). Otherwise, we'd obtain a full SHARE lock. Thus > we'd always lock at least the fields the user told us to, but sometimes more > than those, for the sake of a more efficient implementation.
The problem with this idea is that it's not possible to implement it. -- Álvaro Herrera <alvhe...@commandprompt.com> The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
