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.pecsok@profinit.eu <mailto:jan.pecsok@profinit.eu>
> www.profinit.eu <https://www.profinit.eu/>
> 
> <https://www.profinit.eu/>
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com