mitosis gets in the way of simple select #6470
Last updated: 2017-12-14 14:46:07 +0100
Date: 2017-11-16 10:34:03 +0100
When you have a large table and do a simple select, mitosis kicks in and splits up the select in pieces, just to combine the (basically unaltered) pieces again before returning them.
create table t (i) as (select * from sys.generate_series(cast(0 as integer), 10000000, 1));
Both selects use mitosis.
This bug is derived from bug #6462.
Date: 2017-11-16 12:54:56 +0100
Indeed, there is not much value in parallelizing query parts that do not (significantly) reduce the data volume (or do not have worse than linear complexity, or do not have significant CPU cost). We need to find a robust way to detect such situations easily and generically ...
Date: 2017-11-26 18:35:43 +0100
make sure a simple topn(project(basetable)) (or smaller) query isn't parallelised (as its only output production)
Date: 2017-11-26 20:46:37 +0100
For complete details, see https//devmonetdborg/hg/MonetDB?cmd=changeset;node=ffab2b52402d
The text was updated successfully, but these errors were encountered: