I'd make a copy of the table, and test how long the various methods take.
On 6/23/20 10:17 AM, Jason Ralph wrote:
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Hello List,
PostgreSQL 11.8 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (R
ed Hat 4.4.7-23), 64-bit
I am planning an update on a table with 20Million records, I have been researching the best practices. I will remove all indexes and foreign keys prior to the update, however I am not sure if I should use a transaction or not.
My thought process is that a transaction would be easier to recover if something fails, however it would take more time to write to the WAL log in a transaction.
>Are you updating every row in the table?No I am using an update like so: UPDATE members SET regdate='2038-01-18' WHERE regdate='2020-07-07'
DB=# select count(*) from members where regdate = '2020-07-07';
count
----------
17333090
(1 row)
>Are you updating indexed fields? (If not, then leave the indexes and FKs, since they won't be touched.)Just checked regdate is not indexed so I will leave them in place.
Would it make sense to make a back up of the table then execute update without a transaction?
>Always make a backup.Agreed
How would you guys do it?
>It depends on what percentage of the rows are being updated, which columns are being updated and how big the records are.Please see above, thanks
Jason Ralph
From: Ron <ronljohnsonjr@xxxxxxxxx>
Sent: Tuesday, June 23, 2020 10:57 AM
To: pgsql-general@xxxxxxxxxxxxxxxxxxxx
Subject: Re: UPDATE on 20 Million Records Transaction or not?
On 6/23/20 8:32 AM, Jason Ralph wrote:
Hello List,
PostgreSQL 11.8 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (R
ed Hat 4.4.7-23), 64-bit
I am planning an update on a table with 20Million records, I have been researching the best practices. I will remove all indexes and foreign keys prior to the update, however I am not sure if I should use a transaction or not.
My thought process is that a transaction would be easier to recover if something fails, however it would take more time to write to the WAL log in a transaction.
Are you updating every row in the table?
Are you updating indexed fields? (If not, then leave the indexes and FKs, since they won't be touched.)
Would it make sense to make a back up of the table then execute update without a transaction?
Always make a backup.
How would you guys do it?
It depends on what percentage of the rows are being updated, which columns are being updated and how big the records are.
--
Angular momentum makes the world go 'round.
--
Angular momentum makes the world go 'round.
You can try this
First take backup of table then execute below statements.
create table members_temp
as
select <other_columns>,'2038-01-18'
regdate
from
members where regdate = '2020-07-07';
delete from
members
where regdate = '2020-07-07';
insert into
members select * from
members_temp ;
drop table
members_temp;
Regards,
Ganesh Korde.
On Tue, Jun 23, 2020 at 9:06 PM Ron <ronljohnsonjr@xxxxxxxxx> wrote:
