Horton

Re: POC: Sharing record typmods between backends

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>,Thomas Munro <thomas.munro@enterprisedb.com>,Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2017-05-31T18:29:12Z
Lists: pgsql-hackers 

On May 31, 2017 11:28:18 AM PDT, Robert Haas <robertmhaas@gmail.com> wrote:
>On Wed, May 31, 2017 at 1:46 PM, Andres Freund <andres@anarazel.de>
>wrote:
>> On 2017-05-31 13:27:28 -0400, Dilip Kumar wrote:
>>> On Wed, May 31, 2017 at 12:53 PM, Robert Haas
><robertmhaas@gmail.com> wrote:
>>> > Well, SH_TYPE's members SH_ELEMENT_TYPE *data and void
>*private_data
>>> > are not going to work in DSM, because they are pointers.  You can
>>> > doubtless come up with a way around that problem, but I guess the
>>> > question is whether that's actually any better than just using
>DHT.
>>>
>>> Probably I misunderstood the question. I assumed that we need to
>bring
>>> in DHT only for achieving this goal. But, if the question is simply
>>> the comparison of DHT vs simplehash for this particular case then I
>>> agree that DHT is a more appropriate choice.
>>
>> Yea, I don't think simplehash is the best choice here.  It's
>worthwhile
>> to use it for performance critical bits, but using it for everything
>> would just increase code size without much benefit.  I'd tentatively
>> assume that anonymous record type aren't going to be super common,
>and
>> that this is going to be the biggest bottleneck if you use them.
>
>Did you mean "not going to be"?

Err, yes.  Thanks
-- 
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Commits

  1. Remove TupleDesc remapping logic from tqueue.c.

  2. Add support for coordinating record typmods among parallel workers.

  3. Improve division of labor between execParallel.c and nodeGather[Merge].c.

  4. Add minimal regression test for blessed record type transfer.

  5. Consolidate the function pointer types used by dshash.c.

  6. Fix unlikely shared memory leak after failure in dshash_create().

  7. Refactor typcache.c's record typmod hash table.

  8. Add a hash_combine function for mixing hash values.

  9. Backpatch introduction of TupleDescAttr(tupdesc, i).

  10. Partially flatten struct tupleDesc so that it can be used in DSM.

  11. Change tupledesc->attrs[n] to TupleDescAttr(tupledesc, n).