Horton

Re: Patch: Write Amplification Reduction Method (WARM)

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Pavan Deolasee <pavan.deolasee@gmail.com>, Bruce Momjian <bruce@momjian.us>, Jaime Casanova <jaime.casanova@2ndquadrant.com>, Haribabu Kommi <kommi.haribabu@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-21T16:10:06Z
Lists: pgsql-hackers 
On 2017-03-21 08:04:11 -0400, Robert Haas wrote:
> On Tue, Mar 21, 2017 at 6:56 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> >> Hmm, that test case isn't all that synthetic.  It's just a single
> >> column bulk update, which isn't anything all that crazy, and 5-10%
> >> isn't nothing.
> >>
> >> I'm kinda surprised it made that much difference, though.
> >>
> >
> > I think it is because heap_getattr() is not that cheap.  We have
> > noticed the similar problem during development of scan key push down
> > work [1].
> 
> Yeah.  So what's the deal with this?  Is somebody working on figuring
> out a different approach that would reduce this overhead?

I think one reasonable thing would be to use slots here, and use
slot_getsomeattrs(), with a pre-computed offset, for doing the
deforming.  Given that more than one place run into the issue with
deforming cost via heap_*, that seems like something we're going to have
to do.  Additionally the patches I had for JITed deforming all
integrated at the slot layer, so it'd be a good thing from that angle as
well.

Deforming all columns at once would also a boon for the accompanying
index_getattr calls.


Greetings,

Andres Freund

Commits

  1. Implement SortSupport for macaddr data type

  2. Simplify check of modified attributes in heap_update

  3. Remove direct uses of ItemPointer.{ip_blkid,ip_posid}

  4. Fix CatalogTupleInsert/Update abstraction for case of shared indstate.

  5. Provide CatalogTupleDelete() as a wrapper around simple_heap_delete().

  6. Band-aid fix for incorrect use of view options as StdRdOptions.

  7. Update visibility map in the second phase of vacuum.

  8. Avoid having two copies of the HOT-chain search logic.

  9. Postgres95 1.01 Distribution - Virgin Sources