Re: Transaction isolation and constraints

cliff@krumvieda.com wrote:
> Hi, Tom:
>
> >Whichever one manages to get to the index page first will go through.
> >The second one will block waiting to see if the first one commits,
> >and will error out if so --- or proceed, if it aborts.
>
> I see, this makes sense.  What if the two transactions insert rows
> that don't violate the constraint: will they be able to proceed in
> parallel?  Or will one wait for the other, because they both need to
> update the shared index?  I.e., does the mechanism work by waiting for
> one index update to commit before permitting the next?

They proceed in parallel.  Backends wait only on specific rows that
conflict, not the index page.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://postgres.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +