Re: Reading execution plan - first row time vs last row time

On 10/1/24 06:53, Pecsök Ján wrote:
> Dear community,
>
> We see significant difference in explain analyze Actual time in the
> first line of execution plan and Execution time in the last line of
> execution plan. What can be the reason?
>
> For example, first line of execution plan:
>
> Gather  (cost=1038.49..257627100.42 rows=7943222226 width=104) (actual
> time=531.925..3673159.806 rows=7943221053 loops=1)
>
> This is 3673159/1000/60 = 61 minutes
>
> And last 2 lines of execution plan:
>
> Planning Time: 3000.399 ms
>
> Execution Time: 21208130.602 ms
>
> This is : 21208130/1000/60= 353 minutes
>
> What happened in 353 – 61 = 292 minutes? We speculate that disk writes.
> Query possibly written cca 0,75TB of data, by create table as select query.

You will need to show the complete EXPLAIN ANALYZE output as well as query.

>
>
> S pozdravem
>
> *Ján Pecsők*
>
> Tychonova 2, 160 00 Praha
> Mobil: +420 775 942 871
> jan(dot)pecsok(at)profinit(dot)eu <mailto:jan(dot)pecsok(at)profinit(dot)eu>
> www.profinit.eu <https://www.profinit.eu/>
>
> <https://www.profinit.eu/>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com