Method sql_case_identifier_to_expr

datafusion/sql/src/expr/identifier.rs:233–278

(
        &self,
        operand: Option<Box<SQLExpr>>,
        conditions: Vec<CaseWhen>,
        else_result: Option<Box<SQLExpr>>,
        schema: &DFSchema,
        planner_context: &mut PlannerCo

    }

    pub(super) fn sql_case_identifier_to_expr(
        &self,
        operand: Option<Box<SQLExpr>>,
        conditions: Vec<CaseWhen>,
        else_result: Option<Box<SQLExpr>>,
        schema: &DFSchema,
        planner_context: &mut PlannerContext,
    ) -> Result<Expr> {
        let expr = if let Some(e) = operand {
            Some(Box::new(self.sql_expr_to_logical_expr(
                *e,
                schema,
                planner_context,
            )?))
        } else {
            None
        };
        let when_then_expr = conditions
            .into_iter()
            .map(|e| {
                Ok((
                    Box::new(self.sql_expr_to_logical_expr(
                        e.condition,
                        schema,
                        planner_context,
                    )?),
                    Box::new(self.sql_expr_to_logical_expr(
                        e.result,
                        schema,
                        planner_context,
                    )?),
                ))
            })
            .collect::<Result<Vec<_>>>()?;
        let else_expr = if let Some(e) = else_result {
            Some(Box::new(self.sql_expr_to_logical_expr(
                *e,
                schema,
                planner_context,
            )?))
        } else {
            None
        };

        Ok(Expr::Case(Case::new(expr, when_then_expr, else_expr)))
    }
}

// (relation, column name)