Switching the stream from parallel() to sequential() worked in the initial Stream API design, but caused many problems and finally the implementation was changed, so it just turns the parallel flag on and off for the whole pipeline. The current documentation is indeed vague, but it was improved in Java-9:
The stream pipeline is executed sequentially or in parallel depending on the mode of the stream on which the terminal operation is invoked. The sequential or parallel mode of a stream can be determined with the BaseStream.isParallel() method, and the stream's mode can be modified with the BaseStream.sequential() and BaseStream.parallel() operations. The most recent sequential or parallel mode setting applies to the execution of the entire stream pipeline.
-- show running queries (9.2)
SELECT pid, age(clock_timestamp(), query_start), usename, query
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'
ORDER BY query_start desc;
REQUEST: Only when the request comes directly from the client
FORWARD: Only when the request has been forwarded to a component (see Transferring Control to Another Web Component)
INCLUDE: Only when the request is being processed by a component that has been included (see Including Other Resources in the Response)
ERROR: Only when the request is being processed with the error page mechanism (see Handling Servlet Errors)
You can direct the filter to be applied to any combination of the preceding situations by selecting multiple dispatcher types. If no types are specified, the default option is REQUEST.
G. Mishne, and M. de Rijke. Proceedings ot the 7th International Conference on Computer-Assisted Information Retrieval (Recherche d'Information et ses Applications) - RIAO 2004, page 539--554. CID, (April 2004)