Re: Running pg_dump from a slave server - Mailing list pgsql-general

From Sameer Kumar
Subject Re: Running pg_dump from a slave server
Date
Msg-id CADp-Sm6e9OS8NEAhXJrY_xmM9aKy+-dPoQB1sME_sGA+6NpRPw@mail.gmail.com
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In response to Re: Running pg_dump from a slave server  (Patrick B <patrickbakerbr@gmail.com>)
List pgsql-general


On Wed, Aug 17, 2016 at 11:51 AM Patrick B <patrickbakerbr@gmail.com> wrote:


But do you have statements which causes Exclusive Locks? Ignoring them in OLTP won't make your life any easier. 

(Keeping avoiding to get into 'recovery conflict' as your sole goal) If you decide to  run pg_dump from master, it would block such statements which have Exclusive locking. This would cause delays, deadlocks, livelocks etc and it might take a while for your before you can figure out what is going on.

I would say try to find out who is and why is someone creating Exclusive locks.


Yeah! The pg_dump was already running on the master... it's been running for months.. I just wanted to change now to use the slave, but it seems I can't right?


Not unless you find what is causing the conflict or you are ready to live with delay in promotion when master goes down.
 
Exclusive locking - I probably have statements that causes this. Is there any way I could "track" them?

Do you have-

1. DML operations changing large portions of a table at once - it might lead a page level lock which might conflict with SELECT/share locks on standby
2. Any REINDEX operations
3. DDL operation
4. VACUUM FULL

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Best Regards
Sameer Kumar | DB Solution Architect 
ASHNIK PTE. LTD.

101 Cecil Street, #11-11 Tong Eng Building, Singapore 069 533

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