xudong963 opened a new issue #1228:
URL: https://github.com/apache/arrow-datafusion/issues/1228
**Is your feature request related to a problem or challenge? Please describe
what you are trying to do.**
During I try to implement `Select (subquery)` , I add `
Select(Box<LogicalPlan>)` in `Expr`. Because `Expr` derives `PartialEq,
PartialOrd`, but `LogicalPlan` not, I try to derive `PartialEq, PartialOrd` for
`LogicalPlan`. Unfortunately, I got an error, because some logical plan
contains traits, such as `TableScan`, which contains the `TableProvider` trait.
**Describe the solution you'd like**
In order to achieve better scalability, I think we can extract logical plans
in LogicalPlan as independent structs. For example
```rust
pub enum LogicalPlan {
...
TableScan {
/// The name of the table
table_name: String,
/// The source of the table
source: Arc<dyn TableProvider>,
/// Optional column indices to use as a projection
projection: Option<Vec<usize>>,
/// The schema description of the output
projected_schema: DFSchemaRef,
/// Optional expressions to be used as filters by the table provider
filters: Vec<Expr>,
/// Optional limit to skip reading
limit: Option<usize>,
},
...
}
```
```rust
pub struct TableScanPlan {
/// The name of the table
table_name: String,
/// The source of the table
source: Arc<dyn TableProvider>,
/// Optional column indices to use as a projection
projection: Option<Vec<usize>>,
/// The schema description of the output
projected_schema: DFSchemaRef,
/// Optional expressions to be used as filters by the table provider
filters: Vec<Expr>,
/// Optional limit to skip reading
limit: Option<usize>,
}
pub enum LogicalPlan {
...
TableScan(TableScanPlan),
...
}
```
**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features
you've considered.
**Additional context**
Add any other context or screenshots about the feature request here.
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