Horton

Re: Parallel copy

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Ants Aasma <ants@cybertec.at>, vignesh C <vignesh21@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alastair Turner <minion@decodable.me>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-04-09T19:29:09Z
Lists: pgsql-hackers

Commits

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

  1. Allow WaitLatch() to be used without a latch.

  2. Add %P to log_line_prefix for parallel group leader

  3. Include replication origins in SQL functions for commit timestamp

  4. Avoid useless buffer allocations during binary COPY FROM.

On Thu, Apr 9, 2020 at 2:55 PM Andres Freund <andres@anarazel.de> wrote:
> I'm fairly certain that we do *not* want to distribute input data between processes on a single tuple basis. Probably not even below a few hundred kb. If there's any sort of natural clustering in the loaded data - extremely common, think timestamps - splitting on a granular basis will make indexing much more expensive. And have a lot more contention.

That's a fair point. I think the solution ought to be that once any
process starts finding line endings, it continues until it's grabbed
at least a certain amount of data for itself. Then it stops and lets
some other process grab a chunk of data.

Or are you are arguing that there should be only one process that's
allowed to find line endings for the entire duration of the load?

-- 
Robert Haas
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