hi On Thu, Sep 4, 2014 at 7:01 PM, Robert Haas <robertmh...@gmail.com> wrote: > On Thu, Sep 4, 2014 at 3:09 AM, Ants Aasma <a...@cybertec.at> wrote: >> On Thu, Sep 4, 2014 at 12:36 AM, Andres Freund <and...@2ndquadrant.com> >> wrote: >>> It's imo quite clearly better to keep it allocated. For one after >>> postmaster started the checkpointer successfully you don't need to be >>> worried about later failures to allocate memory if you allocate it once >>> (unless the checkpointer FATALs out which should be exceedingly rare - >>> we're catching ERRORs). It's much much more likely to succeed >>> initially. Secondly it's not like there's really that much time where no >>> checkpointer isn't running. >> >> In principle you could do the sort with the full sized array and then >> compress it to a list of buffer IDs that need to be written out. This >> way most of the time you only need a small array and the large array >> is only needed for a fraction of a second. > > It's not the size of the array that's the problem; it's the size of > the detonation when the allocation fails. > You can use a file backed memory array Or because it's only a hint and - keys are in buffers (BufferTag), right? - transition is only from 'data I care to data I don't care' if a buffer is concurrently evicted when sorting.
Use a pre allocate buffer index array an read keys from buffers when sorting, without memory barrier, spinlocks, whatever. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
