Horton

Re: WIP: [[Parallel] Shared] Hash

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Rafia Sabih <rafia.sabih@enterprisedb.com>
Cc: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, Peter Geoghegan <pg@heroku.com>, Haribabu Kommi <kommi.haribabu@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2017-02-01T19:49:26Z
Lists: pgsql-hackers 
On Thu, Feb 2, 2017 at 3:34 AM, Rafia Sabih
<rafia.sabih@enterprisedb.com> wrote:
> 9         | 62928.88   | 59077.909

Thanks Rafia.  At first glance this plan is using the Parallel Shared
Hash in one place where it should pay off, that is loading the orders
table, but the numbers are terrible.  I noticed that it uses batch
files and then has to increase the number of batch files, generating a
bunch of extra work, even though it apparently overestimated the
number of rows, though that's only ~9 seconds of ~60.  I am
investigating.

-- 
Thomas Munro
http://www.enterprisedb.com

Commits

  1. Add shared tuplestores.

  2. Remove BufFile's isTemp flag.

  3. Provide DSM segment to ExecXXXInitializeWorker functions.

  4. Optimize joins when the inner relation can be proven unique.

  5. Fix failure to use clamp_row_est() for parallel joins.

  6. Document lack of validation when attaching foreign partitions.

  7. Fix inclusions of c.h from .h files.

  8. Fix inclusions of postgres_fe.h from .h files.

  9. Bring plpgsql into line with header inclusion policy.

  10. Document intentional violations of header inclusion policy.

  11. Shut down Gather's children before shutting down Gather itself.

  12. btree: Support parallel index scans.

  13. Add explicit ORDER BY to a few tests that exercise hash-join code.

  14. Revise hash join code so that we can increase the number of batches

  15. Rewrite hash join to use simple linked lists instead of a