Horton

Re: [HACKERS] proposal: schema variables

Dean Rasheed <dean.a.rasheed@gmail.com>

View thread
From: Dean Rasheed <dean.a.rasheed@gmail.com>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Fabien COELHO <coelho@cri.ensmp.fr>, Gilles Darold <gilles.darold@dalibo.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-09-04T07:21:07Z
Lists: pgsql-hackers, pgsql-performance

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Move WAL sequence code into its own file

  2. Add ExplainState argument to pg_plan_query() and planner().

  3. Don't include access/htup_details.h in executor/tuptable.h

  4. Refactor to avoid code duplication in transformPLAssignStmt.

  5. Avoid including commands/dbcommands.h in so many places

  6. Restrict psql meta-commands in plain-text dumps.

  7. Split func.sgml into more manageable pieces

  8. Fix squashing algorithm for query texts

  9. EXPLAIN: Always use two fractional digits for row counts.

  10. Preliminary refactoring of plpgsql expression construction.

  11. plpgsql: pure parser and reentrant scanner

  12. Add some sanity checks in executor for query ID reporting

  13. Fix misleading error message context

  14. Add macros for looping through a List without a ListCell.

AFAICS this patch does nothing to consider parallel safety -- that is,
as things stand, a variable is allowed in a query that may be
parallelised, but its value is not copied to workers, leading to
incorrect results. For example:

create table foo(a int);
insert into foo select * from generate_series(1,1000000);
create variable zero int;
let zero = 0;

explain (costs off) select count(*) from foo where a%10 = zero;

                  QUERY PLAN
-----------------------------------------------
 Finalize Aggregate
   ->  Gather
         Workers Planned: 2
         ->  Partial Aggregate
               ->  Parallel Seq Scan on foo
                     Filter: ((a % 10) = zero)
(6 rows)

select count(*) from foo where a%10 = zero;

 count
-------
 38037    -- Different random result each time, should be 100,000
(1 row)

Thoughts?

Regards,
Dean