andygrove commented on a change in pull request #55:
URL: https://github.com/apache/arrow-datafusion/pull/55#discussion_r619815966
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File path: datafusion/src/logical_plan/expr.rs
##########
@@ -27,14 +27,89 @@ use aggregates::{AccumulatorFunctionImplementation,
StateTypeFunction};
use arrow::{compute::can_cast_types, datatypes::DataType};
use crate::error::{DataFusionError, Result};
-use crate::logical_plan::{DFField, DFSchema};
+use crate::logical_plan::{DFField, DFSchema, DFSchemaRef};
use crate::physical_plan::{
aggregates, expressions::binary_operator_data_type, functions,
udf::ScalarUDF,
};
use crate::{physical_plan::udaf::AggregateUDF, scalar::ScalarValue};
use functions::{ReturnTypeFunction, ScalarFunctionImplementation, Signature};
use std::collections::HashSet;
+/// A named reference to a qualified filed in a schema.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Column {
+ /// relation/table name.
+ pub relation: Option<String>,
+ /// field/column name.
+ pub name: String,
Review comment:
Should we consider supporting compound names here so that we can
eventually support nested types? For example `SELECT t1.customer.address.zip,
...`
Perhaps Column could be an enum?
```rust
enum Column {
Simple(Option<String>, String),
Compound(Option<String>, Vec<String>)
}
```
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