Horton

Re: POC: Sharing record typmods between backends

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Andres Freund <andres@anarazel.de>, Dilip Kumar <dilipbalaut@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2017-08-11T15:14:44Z
Lists: pgsql-hackers 
On Fri, Aug 11, 2017 at 4:39 AM, Thomas Munro
<thomas.munro@enterprisedb.com> wrote:
> OK.  Now it's ds_hash_table.{c,h}, where "ds" stands for "dynamic
> shared".  Better?  If we were to do other data structures in DSA
> memory they could follow that style: ds_red_black_tree.c, ds_vector.c,
> ds_deque.c etc and their identifier prefix would be drbt_, dv_, dd_
> etc.
>
> Do you want to see a separate patch to rename dsa.c?  Got a better
> name?  You could have spoken up earlier :-)  It does sound like a bit
> like the thing from crypto or perhaps a scary secret government
> department.

I doubt that we really want to have accessor functions with names like
dynamic_shared_hash_table_insert or ds_hash_table_insert. Long names
are fine, even desirable, for APIs that aren't too widely used,
because they're relatively self-documenting, but a 30-character
function name gets annoying in a hurry if you have to call it very
often, and this is intended to be reusable for other things that want
a dynamic shared memory hash table.  I think we should (a) pick some
reasonably short prefix for all the function names, like dht or dsht
or ds_hash, but not ds_hash_table or dynamic_shared_hash_table and (b)
also use that prefix as the name for the .c and .h files.

Right now, we've got a situation where the most widely-used hash table
implementation uses dynahash.c for the code, hsearch.h for the
interface, and "hash" as the prefix for the names, and that's really
hard to remember.  I think having a consistent naming scheme
throughout would be a lot better.

-- 
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).