allow queries with filters to use fast-lane reducers

[tyrasd]

Currently, every query which is using a filter (either via an ohsome filter or a custom filter predicate) is using the slower backend routines, because the actual filtering is implemented using flatMap which has a larger overhead than the more streamlined routines which know that no flatMap operations have to be performed.

This has the small side-effect that the NullPointerException from #159 is back (yet, in a different place). But I'd say this is acceptable, as using null values for actual map results should be avoided anyway.

Todo

• compare performance (should be most notable on a query which affects many entities, e.g. type:way and building=* in a country-sized bbox like Germany)
• revert benchmarking-only code (7418f6d)

Checklist

• My code follows the code-style rules, and I have checked on the static analyses and benchmark (if applicable) results
• I have commented my code
• I have written javadoc (required for public classes and methods)
• I have added sufficient unit tests
• I have made corresponding changes to the documentation
• I have updated the CHANGELOG.md
• I have adjusted the examples or created an issue in the corresponding repository
• I have adjusted the benchmark or created an issue in the corresponding repository

[tyrasd]

compare performance

some preliminary results using the ohsome API as a benchmark:

query	local instance of master branch	local instance of #511 branch
type:node and created_by=*, global monthly1	36s	27s
type:way and building=*, Germany bbox, monthly2	1min 22s	59s
type:way and building=*, global, yearly3	2m 49s	2min 27s

Footnotes

1. https://api.ohsome.org/v1/elements/count?bboxes=-180,-90,180,90&filter=type%3Anode%20and%20created_by%3D*&format=json&time=2013-01-01%2F2023-01-01%2FP1M ↩

2. https://api.ohsome.org/v1/elements/count?bboxes=6.2,47,14.9,54.7&filter=type%3Away%20and%20building%3D*&format=json&time=2013-01-01%2F2023-01-01%2FP1M ↩

3. https://api.ohsome.org/v1/elements/count?bboxes=-180,-90,180,90&filter=type%3Away%20and%20building%3D*&format=json&time=2013-01-01%2F2023-01-01%2FP1Y ↩

[rtroilo]

reviewed by peer-review.
Thank you