Re: Death postgres

On 2023-05-10 16:35:04 +0200, Marc Millas wrote:
>  Unique  (cost=72377463163.02..201012533981.80 rows=1021522829864 width=97)
>    ->  Gather Merge  (cost=72377463163.02..195904919832.48 rows=1021522829864 width=97)
...
>                ->  Parallel Hash Left Join  (cost=604502.76..1276224253.51 rows=204304565973 width=97)
>                      Hash Cond: ((t1.col_ano)::text = (t2.col_ano)::text)
...
>
> //so.. the planner guess that those 2 join will generate 1000 billions rows...

Are some of the col_ano values very frequent? If say the value 42 occurs
1 million times in both table_a and table_b, the join will create 1
trillion rows for that value alone. That doesn't explain the crash or the
disk usage, but it would explain the crazy cost (and would probably be a
hint that this query is unlikely to finish in any reasonable time).

        hp

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