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pyarrow_filter_expression.rs
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pyarrow_filter_expression.rs
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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
/// Converts a Datafusion logical plan expression (Expr) into a PyArrow compute expression
use pyo3::prelude::*;
use std::convert::TryFrom;
use std::result::Result;
use arrow::pyarrow::ToPyArrow;
use datafusion::common::{Column, ScalarValue};
use datafusion::logical_expr::{expr::InList, Between, BinaryExpr, Expr, Operator};
use crate::errors::DataFusionError;
#[derive(Debug)]
#[repr(transparent)]
pub(crate) struct PyArrowFilterExpression(PyObject);
fn operator_to_py<'py>(
operator: &Operator,
op: &Bound<'py, PyModule>,
) -> Result<Bound<'py, PyAny>, DataFusionError> {
let py_op: Bound<'_, PyAny> = match operator {
Operator::Eq => op.getattr("eq")?,
Operator::NotEq => op.getattr("ne")?,
Operator::Lt => op.getattr("lt")?,
Operator::LtEq => op.getattr("le")?,
Operator::Gt => op.getattr("gt")?,
Operator::GtEq => op.getattr("ge")?,
Operator::And => op.getattr("and_")?,
Operator::Or => op.getattr("or_")?,
_ => {
return Err(DataFusionError::Common(format!(
"Unsupported operator {operator:?}"
)))
}
};
Ok(py_op)
}
fn extract_scalar_list(exprs: &[Expr], py: Python) -> Result<Vec<PyObject>, DataFusionError> {
let ret: Result<Vec<PyObject>, DataFusionError> = exprs
.iter()
.map(|expr| match expr {
// TODO: should we also leverage `ScalarValue::to_pyarrow` here?
Expr::Literal(v) => match v {
ScalarValue::Boolean(Some(b)) => Ok(b.into_py(py)),
ScalarValue::Int8(Some(i)) => Ok(i.into_py(py)),
ScalarValue::Int16(Some(i)) => Ok(i.into_py(py)),
ScalarValue::Int32(Some(i)) => Ok(i.into_py(py)),
ScalarValue::Int64(Some(i)) => Ok(i.into_py(py)),
ScalarValue::UInt8(Some(i)) => Ok(i.into_py(py)),
ScalarValue::UInt16(Some(i)) => Ok(i.into_py(py)),
ScalarValue::UInt32(Some(i)) => Ok(i.into_py(py)),
ScalarValue::UInt64(Some(i)) => Ok(i.into_py(py)),
ScalarValue::Float32(Some(f)) => Ok(f.into_py(py)),
ScalarValue::Float64(Some(f)) => Ok(f.into_py(py)),
ScalarValue::Utf8(Some(s)) => Ok(s.into_py(py)),
_ => Err(DataFusionError::Common(format!(
"PyArrow can't handle ScalarValue: {v:?}"
))),
},
_ => Err(DataFusionError::Common(format!(
"Only a list of Literals are supported got {expr:?}"
))),
})
.collect();
ret
}
impl PyArrowFilterExpression {
pub fn inner(&self) -> &PyObject {
&self.0
}
}
impl TryFrom<&Expr> for PyArrowFilterExpression {
type Error = DataFusionError;
// Converts a Datafusion filter Expr into an expression string that can be evaluated by Python
// Note that pyarrow.compute.{field,scalar} are put into Python globals() when evaluated
// isin, is_null, and is_valid (~is_null) are methods of pyarrow.dataset.Expression
// https://arrow.apache.org/docs/python/generated/pyarrow.dataset.Expression.html#pyarrow-dataset-expression
fn try_from(expr: &Expr) -> Result<Self, Self::Error> {
Python::with_gil(|py| {
let pc = Python::import_bound(py, "pyarrow.compute")?;
let op_module = Python::import_bound(py, "operator")?;
let pc_expr: Result<Bound<'_, PyAny>, DataFusionError> = match expr {
Expr::Column(Column { name, .. }) => Ok(pc.getattr("field")?.call1((name,))?),
Expr::Literal(scalar) => Ok(scalar.to_pyarrow(py)?.into_bound(py)),
Expr::BinaryExpr(BinaryExpr { left, op, right }) => {
let operator = operator_to_py(op, &op_module)?;
let left = PyArrowFilterExpression::try_from(left.as_ref())?.0;
let right = PyArrowFilterExpression::try_from(right.as_ref())?.0;
Ok(operator.call1((left, right))?)
}
Expr::Not(expr) => {
let operator = op_module.getattr("invert")?;
let py_expr = PyArrowFilterExpression::try_from(expr.as_ref())?.0;
Ok(operator.call1((py_expr,))?)
}
Expr::IsNotNull(expr) => {
let py_expr = PyArrowFilterExpression::try_from(expr.as_ref())?
.0
.into_bound(py);
Ok(py_expr.call_method0("is_valid")?)
}
Expr::IsNull(expr) => {
let expr = PyArrowFilterExpression::try_from(expr.as_ref())?
.0
.into_bound(py);
// https://arrow.apache.org/docs/python/generated/pyarrow.dataset.Expression.html#pyarrow.dataset.Expression.is_null
// Whether floating-point NaNs are considered null.
let nan_is_null = false;
let res = expr.call_method1("is_null", (nan_is_null,))?;
Ok(res)
}
Expr::Between(Between {
expr,
negated,
low,
high,
}) => {
let expr = PyArrowFilterExpression::try_from(expr.as_ref())?.0;
let low = PyArrowFilterExpression::try_from(low.as_ref())?.0;
let high = PyArrowFilterExpression::try_from(high.as_ref())?.0;
let and = op_module.getattr("and_")?;
let le = op_module.getattr("le")?;
let invert = op_module.getattr("invert")?;
// scalar <= field() returns a boolean expression so we need to use and to combine these
let ret = and.call1((
le.call1((low, expr.clone_ref(py)))?,
le.call1((expr, high))?,
))?;
Ok(if *negated { invert.call1((ret,))? } else { ret })
}
Expr::InList(InList {
expr,
list,
negated,
}) => {
let expr = PyArrowFilterExpression::try_from(expr.as_ref())?
.0
.into_bound(py);
let scalars = extract_scalar_list(list, py)?;
let ret = expr.call_method1("isin", (scalars,))?;
let invert = op_module.getattr("invert")?;
Ok(if *negated { invert.call1((ret,))? } else { ret })
}
_ => Err(DataFusionError::Common(format!(
"Unsupported Datafusion expression {expr:?}"
))),
};
Ok(PyArrowFilterExpression(pc_expr?.into()))
})
}
}