Horton

Re: WIP: [[Parallel] Shared] Hash

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, 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: 2017-03-08T00:15:28Z
Lists: pgsql-hackers 
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.

In short, don't even think of doing this.

			regards, tom lane

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