Internal #751: Shared Window Partition

[hawkfish]

• Extend the partitioning and window internals to handle multiple partial sorts.
• Add CSE and and fix BoundWindowExpression::Equals in the process.
• Add partition fusion.

[hawkfish]

fixes: duckdblabs/duckdb-internal#751

[Mytherin]

Thanks for the PR! Could we add some tests with shared partitions/orderings? I'm not sure if this is tested enough by the base set of tests. I've tried this myself and found what I believe to be at least one incorrect result:

CALL dbgen(sf=0.01);
select l_extendedprice, l_partkey, l_orderkey, sum(l_extendedprice) over(order by l_partkey), sum(l_extendedprice) over (order by l_partkey, l_orderkey) from lineitem order by l_partkey, l_orderkey;

This PR

┌─────────────────┬───────────┬────────────┬───────────────┬────────────────┐
│ l_extendedprice │ l_partkey │ l_orderkey │   sum_part    │ sum_part_order │
│  decimal(15,2)  │   int32   │   int32    │ decimal(38,2) │ decimal(38,2)  │
├─────────────────┼───────────┼────────────┼───────────────┼────────────────┤
│        29733.00 │         1 │       2883 │      29733.00 │       29733.00 │
│         1802.00 │         1 │       5121 │      31535.00 │       31535.00 │
│         4505.00 │         1 │       6179 │      36040.00 │       36040.00 │
│            ·    │         · │         ·  │          ·    │           ·    │
│            ·    │         · │         ·  │          ·    │           ·    │
│            ·    │         · │         ·  │          ·    │           ·    │
│        20746.00 │      2000 │      58916 │ 2152182544.47 │  2152182544.47 │
│         7216.00 │      2000 │      59269 │ 2152189760.47 │  2152189760.47 │
├─────────────────┴───────────┴────────────┴───────────────┴────────────────┤
│ 60175 rows (5 shown)                                            5 columns │
└───────────────────────────────────────────────────────────────────────────┘

0.9.2

┌─────────────────┬───────────┬────────────┬───────────────┬────────────────┐
│ l_extendedprice │ l_partkey │ l_orderkey │   sum_part    │ sum_part_order │
│  decimal(15,2)  │   int32   │   int32    │ decimal(38,2) │ decimal(38,2)  │
├─────────────────┼───────────┼────────────┼───────────────┼────────────────┤
│        29733.00 │         1 │       2883 │     607274.00 │       29733.00 │
│         1802.00 │         1 │       5121 │     607274.00 │       31535.00 │
│         4505.00 │         1 │       6179 │     607274.00 │       36040.00 │
│            ·    │         · │         ·  │         ·     │           ·    │
│            ·    │         · │         ·  │         ·     │           ·    │
│            ·    │         · │         ·  │         ·     │           ·    │
│        20746.00 │      2000 │      58916 │ 2152189760.47 │  2152182544.47 │
│         7216.00 │      2000 │      59269 │ 2152189760.47 │  2152189760.47 │
├─────────────────┴───────────┴────────────┴───────────────┴────────────────┤
│ 60175 rows (5 shown)                                            5 columns │
└───────────────────────────────────────────────────────────────────────────┘

[hawkfish]

Even worse, this still gives the right answer:

select 
	l_extendedprice, 
	l_partkey, 
	l_orderkey, 
	sum(l_extendedprice) over (order by l_partkey), 
from lineitem 
order by l_partkey, l_orderkey

[hawkfish]

Sorry about that! Dumb problem in an unexpected place. Restricting to l_partkey = 1 gives a simple repro.

[Mytherin]

Thanks! LGTM