Horton

Re: POC: Sharing record typmods between backends

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2017-05-31T14:57:49Z
Lists: pgsql-hackers 
On Tue, May 30, 2017 at 2:45 AM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> On Tue, May 30, 2017 at 1:09 AM, Thomas Munro
> <thomas.munro@enterprisedb.com> wrote:
>>> * Perhaps simplehash + an LWLock would be better than dht, but I
>>> haven't looked into that.  Can it be convinced to work in DSA memory
>>> and to grow on demand?
>
> Simplehash provides an option to provide your own allocator function
> to it. So in the allocator function, you can allocate memory from DSA.
> After it reaches some threshold it expands the size (double) and it
> will again call the allocator function to allocate the bigger memory.
> You can refer pagetable_allocate in tidbitmap.c.

That only allows the pagetable to be shared, not the hash table itself.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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).