Thread: Regarding vacuum freeze locking mechanism
Hi
Do new inserts block while performing vacuum freeze operations ?
when autovacuum runs , it will freeze the transaction ID (TXID) of the table it's working on. This means that any transactions that started before autovacuum began will be allowed to complete.but new transactions will be blocked until the autovacuum finishes.
Could you please provide more clarity on this? Which lock triggers on the tables are being used by freeze?
Your response is highly appreciated
Regards,
Durga Mahesh
Hi
On Thu, Jul 18, 2024 at 10:26 AM Durgamahesh Manne <maheshpostgres9@gmail.com> wrote:
HiDo 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.
when autovacuum runs , it will freeze the transaction ID (TXID) of the table it's working on. This means that any transactions that started before autovacuum began will be allowed to complete.but new transactions will be blocked until the autovacuum finishes.Could you please provide more clarity on this? Which lock triggers on the tables are being used by freeze?Your response is highly appreciatedRegards,Durga Mahesh
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?
Share update exclusive
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:
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?Share update exclusiveDavid J.