Horton

RE: [PoC] pg_upgrade: allow to upgrade publisher node

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Bharath Rupireddy' <bharath.rupireddyforpostgres@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Bruce Momjian <bruce@momjian.us>, Julien Rouhaud <rjuju123@gmail.com>, vignesh C <vignesh21@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>
Date: 2023-09-21T13:24:45Z
Lists: pgsql-hackers 
Dear Bharath,

Thank you for reviewing! Before addressing them, I would like to reply some comments.

> 6.
> +    if (PQntuples(res) != 1)
> +        pg_fatal("could not count the number of logical replication slots");
> +
> 
> Not existing a single logical replication slot an error? I think it
> must be if (PQntuples(res) == 0) return;?
>

The query executes "SELECT count(*)...", IIUC it exactly returns 1 row.

> 7. A nit:
> +    nslots_on_new = atoi(PQgetvalue(res, 0, 0));
> +
> +    if (nslots_on_new)
> 
> Just do if(atoi(PQgetvalue(res, 0, 0)) > 0) and get rid of nslots_on_new?

Note that the vaule would be used for upcoming pg_fatal. I prefer current style
because multiple atoi(PQgetvalue(res, 0, 0)) was not so beautiful.

> 
> 11.
> +# 2. Generate extra WAL records. Because these WAL records do not get
> consumed
> +#     it will cause the upcoming pg_upgrade test to fail.
> +$old_publisher->safe_psql('postgres',
> +    "CREATE TABLE tbl AS SELECT generate_series(1, 10) AS a;"
> +);
> +$old_publisher->stop;
> 
> This might be a recipie for sporadic test failures - how is it
> guaranteed that the newly generated WAL records aren't consumed.

You mentioned at line 118, but at that time logical replication system is not created.
The subscriber is created at line 163.
Therefore WALs would not be consumed automatically.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED

Commits

  1. Fix issues in binary_upgrade_logical_slot_has_caught_up().

  2. Fix a random failure in 003_logical_slots.pl.

  3. Fix a test in 003_logical_slots.

  4. Fix uninitialized slot array access during the upgrade.

  5. Fix the test 003_logical_slots.

  6. Commit b195e6d482 forgot to update meson.build.

  7. Use shorter file names in the upgrade logical slots test.

  8. Migrate logical slots to the new node during an upgrade.

  9. Flush logical slots to disk during a shutdown checkpoint if required.

  10. Prevent possibility of panics during shutdown checkpoint.