Horton

Re: [HACKERS] Parallel tuplesort (for parallel B-Tree index creation)

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Prabhat Sahu <prabhat.sahu@enterprisedb.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Peter Geoghegan <pg@bowt.ie>, Andres Freund <andres@anarazel.de>, Amit Kapila <amit.kapila16@gmail.com>, Thomas Munro <thomas.munro@enterprisedb.com>, Rushabh Lathia <rushabh.lathia@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Corey Huinker <corey.huinker@gmail.com>
Date: 2018-03-07T13:46:36Z
Lists: pgsql-hackers 
On Wed, Mar 7, 2018 at 8:13 AM, Prabhat Sahu <prabhat.sahu@enterprisedb.com>
wrote:

> Hi all,
>
> While testing this feature I found a crash on PG head with parallel create
> index using pgbanch tables.
>
> -- GUCs under postgres.conf
> max_parallel_maintenance_workers = 16
> max_parallel_workers = 16
> max_parallel_workers_per_gather = 8
> maintenance_work_mem = 8GB
> max_wal_size = 4GB
>
> ./pgbench -i -s 500 -d postgres
>
> postgres=# create index pgb_acc_idx3 on pgbench_accounts(aid,
> abalance,filler);
> WARNING:  terminating connection because of crash of another server process
> DETAIL:  The postmaster has commanded this server process to roll back the
> current transaction and exit, because another server process exited
> abnormally and possibly corrupted shared memory.
> HINT:  In a moment you should be able to reconnect to the database and
> repeat your command.
> server closed the connection unexpectedly
> This probably means the server terminated abnormally
> before or while processing the request.
> The connection to the server was lost. Attempting reset: Failed.
> !>
>

That makes it look like perhaps one of the worker backends crashed.  Did
you get a message in the logfile that might indicate the nature of the
crash?  Something with PANIC or TRAP, perhaps?

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

Commits

  1. Support parallel btree index builds.

  2. Report an ERROR if a parallel worker fails to start properly.

  3. Transfer state pertaining to pending REINDEX operations to workers.

  4. Add a barrier primitive for synchronizing backends.

  5. Allow DML commands that create tables to use parallel query.

  6. Refactor GetOldestXmin() to use flags

  7. Fix regression in parallel planning against inheritance tables.

  8. Don't create "holes" in BufFiles, in the new logtape code.

  9. Simplify the code for logical tape read buffers.

  10. Fix excessive memory consumption in the new sort pre-reading code.

  11. Implement binary heap replace-top operation in a smarter way.

  12. Cosmetic code cleanup in commands/extension.c.

  13. Speed up planner's scanning for parallel-query hazards.

  14. Read from the same worker repeatedly until it returns no tuple.

  15. Improve tuplesort.c to support variable merge order. The original coding