>> rhaas=# explain select a from generate_series(1,100) a union select a
>> from generate_series(1,100) a;
>> QUERY PLAN
>> --
>> HashAggregate (cost=45.00..65.00 rows=2000 widt
pinker wrote
>>> rhaas=# explain select a from generate_series(1,100) a union select a
>>> from generate_series(1,100) a;
>>> QUERY PLAN
>>> --
>>> HashAggregate (cost=45.00..65
2010/12/12 pasman pasmański :
>> UNION will remove all duplicates, so that the result additionally requires to
>> be sorted.
>
>>Right, to avoid the SORT and UNIQUE - operation you can use UNION ALL
>
>
> by the way maybe apply hashing to calculate UNION be better ?
The planner already considers s
> UNION will remove all duplicates, so that the result additionally requires to
> be sorted.
>Right, to avoid the SORT and UNIQUE - operation you can use UNION ALL
by the way maybe apply hashing to calculate UNION be better ?
pasman
--
Sent via pgsql-performance mailing list (pg
Marc Mamin wrote:
> Hello,
>
>
>
> UNION will remove all duplicates, so that the result additionally requires to
> be sorted.
Right, to avoid the SORT and UNIQUE - operation you can use UNION ALL
>
> Anyway, for performance issues, you should always start investigation with
> explain ana
Hello,
UNION will remove all duplicates, so that the result additionally
requires to be sorted.
Anyway, for performance issues, you should always start investigation
with explain analyze .
regards,
Marc Mamin
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