jcsherin commented on code in PR #13201:
URL: https://github.com/apache/datafusion/pull/13201#discussion_r1829212628
##########
datafusion/expr/src/built_in_window_function.rs:
##########
@@ -17,115 +17,12 @@
//! Built-in functions module contains all the built-in functions definitions.
-use std::fmt;
-use std::str::FromStr;
-
-use crate::type_coercion::functions::data_types;
-use crate::utils;
-use crate::{Signature, Volatility};
-use datafusion_common::{plan_datafusion_err, plan_err, DataFusionError,
Result};
-
-use arrow::datatypes::DataType;
-
use strum_macros::EnumIter;
-impl fmt::Display for BuiltInWindowFunction {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- write!(f, "{}", self.name())
- }
-}
-
/// A [window function] built in to DataFusion
///
/// [Window Function]: https://en.wikipedia.org/wiki/Window_function_(SQL)
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Hash, EnumIter)]
pub enum BuiltInWindowFunction {
- /// returns value evaluated at the row that is the first row of the window
frame
- FirstValue,
- /// Returns value evaluated at the row that is the last row of the window
frame
- LastValue,
- /// Returns value evaluated at the row that is the nth row of the window
frame (counting from 1); returns null if no such row
- NthValue,
-}
-
-impl BuiltInWindowFunction {
- pub fn name(&self) -> &str {
- use BuiltInWindowFunction::*;
- match self {
- FirstValue => "first_value",
- LastValue => "last_value",
- NthValue => "NTH_VALUE",
- }
- }
-}
-
-impl FromStr for BuiltInWindowFunction {
- type Err = DataFusionError;
- fn from_str(name: &str) -> Result<BuiltInWindowFunction> {
- Ok(match name.to_uppercase().as_str() {
- "FIRST_VALUE" => BuiltInWindowFunction::FirstValue,
- "LAST_VALUE" => BuiltInWindowFunction::LastValue,
- "NTH_VALUE" => BuiltInWindowFunction::NthValue,
- _ => return plan_err!("There is no built-in window function named
{name}"),
- })
- }
-}
-
-/// Returns the datatype of the built-in window function
-impl BuiltInWindowFunction {
- pub fn return_type(&self, input_expr_types: &[DataType]) ->
Result<DataType> {
- // Note that this function *must* return the same type that the
respective physical expression returns
- // or the execution panics.
-
- // Verify that this is a valid set of data types for this function
- data_types(input_expr_types, &self.signature())
- // Original errors are all related to wrong function signature
- // Aggregate them for better error message
- .map_err(|_| {
- plan_datafusion_err!(
- "{}",
- utils::generate_signature_error_msg(
- &format!("{self}"),
- self.signature(),
- input_expr_types,
- )
- )
- })?;
-
- match self {
- BuiltInWindowFunction::FirstValue
- | BuiltInWindowFunction::LastValue
- | BuiltInWindowFunction::NthValue =>
Ok(input_expr_types[0].clone()),
- }
- }
-
- /// The signatures supported by the built-in window function `fun`.
- pub fn signature(&self) -> Signature {
- // Note: The physical expression must accept the type returned by this
function or the execution panics.
- match self {
- BuiltInWindowFunction::FirstValue |
BuiltInWindowFunction::LastValue => {
- Signature::any(1, Volatility::Immutable)
- }
- BuiltInWindowFunction::NthValue => Signature::any(2,
Volatility::Immutable),
- }
- }
-}
-
-#[cfg(test)]
-mod tests {
- use super::*;
- use strum::IntoEnumIterator;
- #[test]
- // Test for BuiltInWindowFunction's Display and from_str() implementations.
- // For each variant in BuiltInWindowFunction, it converts the variant to a
string
- // and then back to a variant. The test asserts that the original variant
and
- // the reconstructed variant are the same. This assertion is also
necessary for
- // function suggestion. See
https://github.com/apache/datafusion/issues/8082
- fn test_display_and_from_str() {
- for func_original in BuiltInWindowFunction::iter() {
- let func_name = func_original.to_string();
- let func_from_str =
BuiltInWindowFunction::from_str(&func_name).unwrap();
- assert_eq!(func_from_str, func_original);
- }
- }
Review Comment:
It will be a good to convert this to a sqllogicttest now. For e.g.,
```sql
> SELECT
NTH_VLUE(c4, 2) OVER()
FROM aggregate_test_100
ORDER BY c9
LIMIT 5;
Error during planning: Invalid function 'nth_vlue'.
Did you mean 'nth_value'?
> SELECT
FRST_VALUE(c4, 2) OVER()
FROM aggregate_test_100
ORDER BY c9
LIMIT 5;
Error during planning: Invalid function 'frst_value'.
Did you mean 'first_value'?
```
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