vegafusion_runtime/transform/
formula.rs

1use crate::expression::compiler::compile;
2use crate::expression::compiler::config::CompilationConfig;
3use crate::transform::TransformTrait;
4
5use vegafusion_core::error::{Result, ResultWithContext};
6use vegafusion_core::proto::gen::transforms::Formula;
7
8use crate::expression::compiler::utils::VfSimplifyInfo;
9use async_trait::async_trait;
10use datafusion::prelude::DataFrame;
11use datafusion_optimizer::simplify_expressions::ExprSimplifier;
12use vegafusion_common::column::flat_col;
13use vegafusion_core::task_graph::task_value::TaskValue;
14
15#[async_trait]
16impl TransformTrait for Formula {
17    async fn eval(
18        &self,
19        dataframe: DataFrame,
20        config: &CompilationConfig,
21    ) -> Result<(DataFrame, Vec<TaskValue>)> {
22        let formula_expr = compile(
23            self.expr.as_ref().unwrap(),
24            config,
25            Some(dataframe.schema()),
26        )?;
27
28        // Simplify expression prior to evaluation
29        let simplifier = ExprSimplifier::new(VfSimplifyInfo::from(dataframe.schema().clone()));
30        let formula_expr = simplifier.simplify(formula_expr)?;
31
32        // Rename with alias
33        let formula_expr = formula_expr.alias(&self.r#as);
34
35        // Build selections. If as field name is already present, replace it with
36        // formula expression at the same position. Otherwise append formula expression
37        // to the end of the selection list
38        let mut selections = Vec::new();
39        let mut as_field_added = false;
40        for field in dataframe.schema().fields().iter() {
41            if field.name() == &self.r#as {
42                selections.push(formula_expr.clone());
43                as_field_added = true;
44            } else {
45                selections.push(flat_col(field.name()))
46            }
47        }
48        if !as_field_added {
49            selections.push(formula_expr);
50        }
51
52        // dataframe
53        let result = dataframe.select(selections).with_context(|| {
54            format!(
55                "Formula transform failed with expression: {}",
56                &self.expr.as_ref().unwrap()
57            )
58        })?;
59
60        Ok((result, Default::default()))
61    }
62}
vegafusion_runtime/transform/formula.rs

vegafusion_runtime/transform/
formula.rs
