Re: ALTER TABLE ADD COLUMN takes forever

I know your pain well. It is because you set a default value for the column, so it has to initialise that value for every role. If you don’t set a default, it should be quite expedient, so you have to weigh that.

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Sent from mobile, with due apologies for brevity and errors.

> On Mar 29, 2021, at 1:08 PM, Devendra Yadav <devendra(dot)857(at)gmail(dot)com> wrote:
>
> 
> Hello Experts,
>
> I am running a query on a table - ALTER TABLE mytable ADD COLUMN deposited DOUBLE PRECISION DEFAULT 0.0;
>
> this query just runs forever. Few more details about this table -
> Total row count - 300000 (a small table of 200MB)
> Columns - 42
> Indexes - 15
> Foreign key constraint - 14
> Table reference - 11
>
> When i check for the query in pg_stat_activity the wait even is LOCK and wait_event_type is RELATION.
> Also when i check in pg_locks the granted status is 'f'. However there are no pid's blocking this transaction.
>
> This has just 500 dead tuples, so no problems there as well
>
> I am a DBA and not good at development.
> Unable to understand what would be causing this? Could you guys help me what should be my next approach or solutions on this .
>
> Regards,
> Devendra Yadav