Re: Transaction isolation and constraints

cliff(at)krumvieda(dot)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(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://postgres.enterprisedb.com

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