On Fri, May 25, 2012 at 3:04 PM, Ivan Voras <ivoras@xxxxxxxxxxx> wrote: > Hello, > > I'm wondering if there is ia document describing which guarantees (if > any) PostgreSQL makes about concurrency for various operations? Speaking > in general (i.e. IO can handle it, number of CPU cores and client > threads is optimal), are fully concurrent operations (independant and > non-blocking) possible for: By "fully concurrent" do you mean that there is no detectable sub-linear scaling at all? I'm pretty sure that no such guarantees can be made. > 1) An unindexed table? For concurrent bulk loads, there was severe contention on generating WAL between concurrent bulk loaders. That is greatly improved in the upcoming 9.2 release. > 2) A table with 1+ ordinary (default btree) indexes? (are there > constraints on the structure and number of indexes?) This will be limited by contention for generating WAL. (Unless something else limits it first) > 3) A table with 1+ unique indexes? If more than one transaction attempts to insert the same value, one has to block until the other either commits or rollbacks. > 4) A table with other objects on it (foreign keys, check constraints, etc.)? Same as above. If they try to do conflicting things, they don't continue operating concurrently. Cheers, Jeff -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
