xudong963 commented on pull request #1566:
URL:
https://github.com/apache/arrow-datafusion/pull/1566#issuecomment-1013877492
> Could you possibly provide some tests @xudong963 ?
Sure.
> I was expecting to see code that basically applied an algebraic
transformation on predicates like:
The ticket doesn't do the transformation. It does the following thing.
First of all, let's see the example:
```
❯ create table part as select 1 as p_partkey;
0 rows in set. Query took 0.003 seconds.
❯ create table lineitem as select 1 as l_partkey, 2 as l_suppkey;
0 rows in set. Query took 0.005 seconds.
❯ create table supplier as select 1 as s_suppkey;
0 rows in set. Query took 0.002 seconds.
❯ explain select * from part, supplier, lineitem where p_partkey = l_partkey
and s_suppkey = l_suppkey;
+---------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------+
| plan_type | plan
|
+---------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------+
| logical_plan | Projection: #part.p_partkey, #supplier.s_suppkey,
#lineitem.l_partkey, #lineitem.l_suppkey
|
| | Join: #part.p_partkey = #lineitem.l_partkey,
#supplier.s_suppkey = #lineitem.l_suppkey
|
| | CrossJoin:
|
| | TableScan: part projection=Some([0])
|
| | TableScan: supplier projection=Some([0])
|
| | TableScan: lineitem projection=Some([0, 1])
```
https://github.com/apache/arrow-datafusion/blob/6f7b2d25fb75c843efed67fbd72d09b2c2d6c2eb/datafusion/src/sql/planner.rs#L718
In the `for` loop, at first, `left` is `part`, `right` is `supplier`, there
is no `join key` between `part` and `right`, so result in `cross join` between
`part` and `right`. It's heavy.
In the ticket, we can push `supplier` to `mut_plans`, after inner join
`part` and `lineitem`, `supplier` can inner join with them.
```
+---------------+----------------------------------------------------------------------------------------------------------------------------------------------------+
| plan_type | plan
|
+---------------+----------------------------------------------------------------------------------------------------------------------------------------------------+
| logical_plan | Projection: #part.p_partkey, #lineitem.l_partkey,
#lineitem.l_suppkey, #supplier.s_suppkey
|
| | Join: #lineitem.l_suppkey = #supplier.s_suppkey
|
| | Join: #part.p_partkey = #lineitem.l_partkey
|
| | TableScan: part projection=Some([0])
|
| | TableScan: lineitem projection=Some([0, 1])
|
| | TableScan: supplier projection=Some([0])
```
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