Horton

Re: WIP: [[Parallel] Shared] Hash

Peter Geoghegan <pg@heroku.com>

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From: Peter Geoghegan <pg@heroku.com>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Haribabu Kommi <kommi.haribabu@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2017-01-02T02:17:12Z
Lists: pgsql-hackers 
On Sat, Dec 31, 2016 at 2:52 AM, Thomas Munro
<thomas.munro@enterprisedb.com> wrote:
> Unfortunately it's been a bit trickier than I anticipated to get the
> interprocess batch file sharing and hash table shrinking working
> correctly and I don't yet have a new patch in good enough shape to
> post in time for the January CF.  More soon.

I noticed a bug in your latest revision:

> +   /*
> +    * In HJ_NEED_NEW_OUTER, we already selected the current inner batch for
> +    * reading from.  If there is a shared hash table, we may have already
> +    * partially loaded the hash table in ExecHashJoinPreloadNextBatch.
> +    */
> +   Assert(hashtable->batch_reader.batchno = curbatch);
> +   Assert(hashtable->batch_reader.inner);

Obviously this isn't supposed to be an assignment.

-- 
Peter Geoghegan

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