Parallelise scanning result of ORDER_BY #5403
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Mytherin
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Nov 18, 2022
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Thanks for the PR! Looks good to me. Could we add some tests, particularly around verifying that the results are actually stored in the correct order, also with persistent storage?
One way of testing this is to use window functions without an explicit order by, e.g.:
create table integers(i integer);
insert into integers values (1), (2), (3);
-- check that either the row is the first row, or the value of "i" is bigger than the last row
-- this should return an empty result because of the NOT
select * FROM integers QUALIFY NOT (i>=lag(i) over () OR lag(i) OVER () IS NULL);Add support for reading JSON type columns from Parquet files
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This is ready to go, I will push the bugfix we discussed to master |
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Thanks! |
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This PR implements parallel scanning of the result of the ORDER_BY operator. Preserving the order while reading sorted data has been made possible by adding batch indices to local scan states. It was very easy to implement with all this infrastructure in place. Thanks, @Mytherin!
Quick benchmark, of course.
Timing in seconds (on my laptop):
As we can see, sorted tables can be created much more quickly, which can help with zone maps, for example.
This also makes it more enticing to use the
PhysicalOrderoperator for index creation (CC @taniabogatsch)