Horton

Re: Parallel Append implementation

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
Cc: Amit Khandekar <amitdkhan.pg@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-16T19:14:55Z
Lists: pgsql-hackers 
On Thu, Mar 16, 2017 at 8:48 AM, Ashutosh Bapat
<ashutosh.bapat@enterprisedb.com> wrote:
> Why do we need following code in both ExecAppendInitializeWorker() and
> ExecAppendInitializeDSM()? Both of those things happen before starting the
> actual execution, so one of those should suffice?
> +    /* Choose the optimal subplan to be executed. */
> +    (void) parallel_append_next(node);

ExecAppendInitializeWorker runs only in workers, but
ExecAppendInitializeDSM runs only in the leader.

> BTW, sa_finished seems to be a misnomor. The plan is not finished yet, but it
> wants no more workers. So, should it be renamed as sa_no_new_workers or
> something like that?

I think that's not going to improve clarity.  The comments can clarify
the exact semantics.

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

Commits

  1. Update parallel.sgml for Parallel Append

  2. Support Parallel Append plan nodes.

  3. Remove BufFile's isTemp flag.

  4. Improve comments for parallel executor estimation functions.

  5. Separate reinitialization of shared parallel-scan state from ExecReScan.

  6. Eat XIDs more efficiently in recovery TAP test.

  7. Avoid syntax error on platforms that have neither LOCALE_T nor ICU.

  8. Preparatory refactoring for parallel merge join support.