Regarding vacuum freeze locking mechanism

Hi

On Thu, Jul 18, 2024 at 10:26 AM Durgamahesh Manne <
maheshpostgres9@gmail.com> wrote:

Hi

Do new inserts block while performing vacuum freeze operations ?

Generally, VACUUM FREEZE does not block inserts as PG uses Multi-Version
Concurrency Control (MVCC) which allows multiple transactions to operate on
the same table without interfering with each other.

On Wednesday, July 17, 2024, Durgamahesh Manne <maheshpostgres9@gmail.com>
wrote:

when autovacuum runs , it will freeze the transaction ID (TXID) of the
table it's working on.

This statement is incorrect. A table as a whole does not have a txid.
Freezing makes it so individual tuples get assigned an always-in-the-past
txid. Then, the table can recompute how far away its furthest back txid is
from being considered in-the-future. That gap should increase since the
furthest away txids were the ones being frozen.

Inserts might get delayed a brief moment if it just happens the page they
want to insert onto is presently being worked on. But the odds there seem
low.

David J.

On Wednesday, July 17, 2024, Durgamahesh Manne <maheshpostgres9@gmail.com>
wrote:

Could you please provide more clarity on this? Which lock triggers on the
tables are being used by freeze?

https://www.postgresql.org/docs/current/explicit-locking.html

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David J.

Hi David.

Excellent response from you .Great

Regards,
Durga Mahesh

On Thu, Jul 18, 2024 at 11:28 AM David G. Johnston <
david.g.johnston@gmail.com> wrote: