Horton

Re: Patch: Write Amplification Reduction Method (WARM)

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Amit Kapila <amit.kapila16@gmail.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: 2017-03-21T14:40:43Z
Lists: pgsql-hackers 
On Tue, Mar 21, 2017 at 10:21 AM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Robert Haas wrote:
>> On Tue, Mar 21, 2017 at 10:01 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>
>> > Sure, we can try that.  I think we need to try it with
>> > synchronous_commit = off, otherwise, WAL writes completely overshadows
>> > everything.
>>
>> synchronous_commit = off is a much more realistic scenario than fsync = off.
>
> Sure, synchronous_commit=off is a reasonable case.  But I say if we lose
> a few % on the case where you update only the first indexed of a large
> number of very wide columns all indexed, and this is only noticeable if
> you don't write WAL and only if you update all the rows in the table,
> then I don't see much reason for concern.

If the WAL writing hides the loss, then I agree that's not a big
concern.  But if the loss is still visible even when WAL is written,
then I'm not so sure.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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