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Re: Sequential parallel scan / agg

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Hi,

On 2016-11-13 23:04:44 +0000, James Sewell said:
> 	1.	INSERT ... SELECT doesn't work
> 	2.	WITH a AS (SELECT ...) INSERT FROM a doesn't work
> 	3.	SELECT .. INTO doesn't work
> 	4.	SELECT with no insert does work as expected
>> 
>> CREATE TABLE blah AS SELECT ...  ?

Unfortunately, in these cases the current parallelism features cannot be used as all of these queries do write data. See in the doc [1] at "When Can Parallel Query Be Used?" 

> Even when it is in general possible for parallel query plans to be generated, the planner will not generate them for a given query if any of the following are true:
> 	•	The query writes any data or locks any database rows. If a query contains a data-modifying operation either at the top level or within a CTE, no parallel plans for that query will be generated. This is a limitation of the current implementation which could be lifted in a future release.

Best
Tobias

[1]: https://www.postgresql.org/docs/current/static/when-can-parallel-query-be-used.html



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