Make ORDER BY tuple almost as fast as ORDER BY columns #34060
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We have special optimizations for multiple column ORDER BY: ClickHouse#10831 . It's beneficial to also apply to tuple columns. Before: select * from numbers(300000000) order by (1 - number , number + 1 , number) limit 10; 2.613 sec. After: select * from numbers(300000000) order by (1 - number , number + 1 , number) limit 10; 0.755 sec No tuple: select * from numbers(300000000) order by 1 - number , number + 1 , number limit 10; 0.755 sec
robot-clickhouse
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kitaisreal
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Jan 29, 2022
src/Interpreters/sortBlock.cpp
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| ErrorCodes::BAD_COLLATION); | ||
| } | ||
| if (const auto * tuple = typeid_cast<const ColumnTuple *>(column)) | ||
| flattenTupleColumnRecursively(res, tuple, &description[i], isColumnConst(*column)); |
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I am not sure if we need to make a lot of changes.
Currently for each column in ColumnTuple we can create own ColumnSortDescription just copy input ColumnSortDescription, remove Collation if needed (for non String types), and then other code will work as expected.
kitaisreal
approved these changes
Jan 29, 2022
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Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
Make ORDER BY tuple almost as fast as ORDER BY columns. We have special optimizations for multiple column ORDER BY: #10831 . It's beneficial to also apply to tuple columns.
It's still not 100% the same because we have other optimization techniques like
optimize_monotonous_functions_in_order_by, which is not applied to inner columns of a tuple. But it's good enough.