Horton

Re: WIP: [[Parallel] Shared] Hash

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>, Rafia Sabih <rafia.sabih@enterprisedb.com>, Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, Peter Geoghegan <pg@heroku.com>, Haribabu Kommi <kommi.haribabu@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-08T21:54:06Z
Lists: pgsql-hackers 
On Wed, Mar 8, 2017 at 1:15 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Andres Freund <andres@anarazel.de> writes:
>> +++ b/src/include/storage/barrier.h
>> +#include "postgres.h"
>
>> Huh, that normally shouldn't be in a header.  I see you introduced that
>> in a bunch of other places too - that really doesn't look right to me.
>
> That is absolutely not project style and is not acceptable.
>
> The core reason why not is that postgres.h/postgres_fe.h/c.h have to be
> the *first* inclusion in every compilation, for arcane portability reasons
> you really don't want to know about.  (Suffice it to say that on some
> platforms, stdio.h isn't all that std.)  Our coding rule for that is that
> we put the appropriate one of these first in every .c file, while .h files
> always assume that it's been included already.  As soon as you break that
> convention, it becomes unclear from looking at a .c file whether the
> ordering requirement has been satisfied.  Also, since now you've moved
> the must-be-first requirement to some other header file(s), you risk
> breakage when somebody applies another project convention about
> alphabetizing #include references for all headers other than those magic
> ones.

Thanks for the explanation.  Will post a new series addressing this
and other complaints from Andres shortly.

-- 
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