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Groupby and Aggregates - Instructions and Codegen overhaul #26
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Are there test cases illustrating what code will be generated given the sample SQL we use in the blog post? |
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Not yet. I'm working on it currently. |
Not yet done for Function
commented out the original version for reference
but are they correct?
Samyak2
commented
May 8, 2023
There was a problem hiding this comment.
This is now complete. Took a lot longer than expected :(
For this query:
select
col1,
col3 + 1,
max(col2) + 1,
count(1) as count
from abc
group by col1, col3This is the generated code:
Source { index: %0, name: abc }
Empty { index: %1 }
Project { input: %0, output: %1, expr: column 'col2', alias: __otter_temp_col_1 }
Project { input: %0, output: %1, expr: 1, alias: __otter_temp_col_3 }
Empty { index: %2 }
GroupBy { input: %1, output: %2, expr: column 'col1' }
Empty { index: %3 }
GroupBy { input: %2, output: %3, expr: column 'col3' }
Empty { index: %4 }
Aggregate { input: %3, output: %4, func: Agg(max), col_name: __otter_temp_col_1, alias: __otter_temp_col_2 }
Aggregate { input: %3, output: %4, func: Agg(count), col_name: __otter_temp_col_3, alias: __otter_temp_col_4 }
Empty { index: %5 }
Project { input: %0, output: %5, expr: column 'col1', alias: None }
Project { input: %0, output: %5, expr: (column 'col3' + 1), alias: None }
Project { input: %4, output: %5, expr: (column '__otter_temp_col_2' + 1), alias: None }
Project { input: %4, output: %5, expr: column '__otter_temp_col_4', alias: count }
Return { index: %5 }
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Interesting, is there an example for the following too? select
col1,
col3 + 1,
max(col2 + 1)
from abc
group by col1, col3 |
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Description
We took a second look at the
GroupByinstruction and found it very lacking (see #16). This PR represents an overhaul of it.Partially fixes #24
Changes
Aggregateinstruction to calculate aggregations on a grouped tableCodegenContextstruct to make passing them around easier.GroupBywill now produce a grouped table which will be lazily evaluated. Note: the evaluation is not in scope for this PR.Some questions/concerns