datafusion/physical-expr/src/expressions/unknown_column.rs

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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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//! UnKnownColumn expression

use std::any::Any;
use std::hash::{Hash, Hasher};
use std::sync::Arc;

use crate::PhysicalExpr;

use arrow::{
    datatypes::{DataType, Schema},
    record_batch::RecordBatch,
};
use datafusion_common::{internal_err, Result};
use datafusion_expr::ColumnarValue;

#[derive(Debug, Clone, Eq)]
pub struct UnKnownColumn {
    name: String,
}

impl UnKnownColumn {
    /// Create a new unknown column expression
    pub fn new(name: &str) -> Self {
        Self {
            name: name.to_owned(),
        }
    }

    /// Get the column name
    pub fn name(&self) -> &str {
        &self.name
    }
}

impl std::fmt::Display for UnKnownColumn {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{}", self.name)
    }
}

impl PhysicalExpr for UnKnownColumn {
    /// Return a reference to Any that can be used for downcasting
    fn as_any(&self) -> &dyn Any {
        self
    }

    /// Get the data type of this expression, given the schema of the input
    fn data_type(&self, _input_schema: &Schema) -> Result<DataType> {
        Ok(DataType::Null)
    }

    /// Decide whether this expression is nullable, given the schema of the input
    fn nullable(&self, _input_schema: &Schema) -> Result<bool> {
        Ok(true)
    }

    /// Evaluate the expression
    fn evaluate(&self, _batch: &RecordBatch) -> Result<ColumnarValue> {
        internal_err!("UnKnownColumn::evaluate() should not be called")
    }

    fn children(&self) -> Vec<&Arc<dyn PhysicalExpr>> {
        vec![]
    }

    fn with_new_children(
        self: Arc<Self>,
        _children: Vec<Arc<dyn PhysicalExpr>>,
    ) -> Result<Arc<dyn PhysicalExpr>> {
        Ok(self)
    }

    fn fmt_sql(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        std::fmt::Display::fmt(self, f)
    }
}

impl Hash for UnKnownColumn {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.name.hash(state);
    }
}

impl PartialEq for UnKnownColumn {
    fn eq(&self, _other: &Self) -> bool {
        // UnknownColumn is not a valid expression, so it should not be equal to any other expression.
        // See https://github.com/apache/datafusion/pull/11536
        false
    }
}