Re: Adding new field to big table

Hello,

Jeff and Jeffrey thank you for your tips.
This is the explain of the query:
x=> explain update document as d set "svmConfidence" = st.svmconfidence from svm_confidence_id_tmp as st where st.id = d.id;
QUERY PLAN
---------------------------------------------------------------------------------------------------------
Update on document d (cost=4204242.82..61669685.86 rows=124515592 width=284)
-> Hash Join (cost=4204242.82..61669685.86 rows=124515592 width=284)
Hash Cond: (d.id = st.id)
-> Seq Scan on document d (cost=0.00..8579122.97 rows=203066697 width=270)
-> Hash (cost=1918213.92..1918213.92 rows=124515592 width=18)
-> Seq Scan on svm_confidence_id_tmp st (cost=0.00..1918213.92 rows=124515592 width=18)
(6 rows)

It's not using the index, most of the rows are beeing updated.
I'm trying with the CTAS solution.

Cheers,
Andrés.

El Mar 14, 2014, a las 8:29 PM, Jeff Janes escribió:

> On Fri, Mar 14, 2014 at 10:06 AM, acanada <acanada(at)cnio(dot)es> wrote:
> Hello Jeff,
>
> The lock time is not a problem. The problem is that takes too much time. I will need to add more fields to this table in the near future and I'd like to know if the process can be accelerated by any parameter, workaround or whatever...
>
> Thank you for your answer.
>
> OK. Can you provide an explain (analyze, buffers), and the other information described here: http://wiki.postgresql.org/wiki/Slow_Query_Questions
>
> It may be faster to make a new table by selecting a join on the existing tables and then replace the master table with it.
>
> Also, if you are going to be doing a lot of bulk updates like this, lowering the fillfactor to below 50% might be helpful.
>
> Cheers,
>
> Jeff
>

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