izveigor commented on code in PR #7220:
URL: https://github.com/apache/arrow-datafusion/pull/7220#discussion_r1286712027
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datafusion/expr/src/field_util.rs:
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@@ -20,64 +20,65 @@
use arrow::datatypes::{DataType, Field};
use datafusion_common::{plan_err, DataFusionError, Result, ScalarValue};
-pub enum GetFieldAccessCharacteristic {
- /// returns the field `struct[field]`. For example `struct["name"]`
+/// Types of the field access expression of a nested type, such as `Field` or
`List`
+pub enum GetFieldAccessSchema {
+ /// Named field, For example `struct["name"]`
NamedStructField { name: ScalarValue },
- /// single list index
- // list[i]
+ /// Single list index, for example: `list[i]`
ListIndex { key_dt: DataType },
- /// list range `list[i:j]`
+ /// List range, for example `list[i:j]`
ListRange {
start_dt: DataType,
stop_dt: DataType,
},
}
-/// Returns the field access indexed by `key` and/or `extra_key` from a
[`DataType::List`] or [`DataType::Struct`]
-/// # Error
-/// Errors if
-/// * the `data_type` is not a Struct or a List,
-/// * the `data_type` of extra key does not match with `data_type` of key
-/// * there is no field key is not of the required index type
-pub fn get_indexed_field(
- data_type: &DataType,
- field_characteristic: &GetFieldAccessCharacteristic,
-) -> Result<Field> {
- match field_characteristic {
- GetFieldAccessCharacteristic::NamedStructField{ name } => {
- match (data_type, name) {
- (DataType::Struct(fields), ScalarValue::Utf8(Some(s))) => {
- if s.is_empty() {
- plan_err!(
- "Struct based indexed access requires a non empty
string"
- )
- } else {
- let field = fields.iter().find(|f| f.name() == s);
- field.ok_or(DataFusionError::Plan(format!("Field {s}
not found in struct"))).map(|f| f.as_ref().clone())
+impl GetFieldAccessSchema {
+ /// Returns the schema [`Field`] from a [`DataType::List`] or
+ /// [`DataType::Struct`] indexed by this structure
+ ///
+ /// # Error
+ /// Errors if
+ /// * the `data_type` is not a Struct or a List,
+ /// * the `data_type` of extra key does not match with `data_type` of key
Review Comment:
It is better to replace `extra_key` and `key` with new terms
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