Method sql_expr_to_logical_expr

datafusion/sql/src/expr/mod.rs:71–122

(
        &self,
        sql: SQLExpr,
        schema: &DFSchema,
        planner_context: &mut PlannerContext,
    )

        Ok(expr)
    }
    pub(crate) fn sql_expr_to_logical_expr(
        &self,
        sql: SQLExpr,
        schema: &DFSchema,
        planner_context: &mut PlannerContext,
    ) -> Result<Expr> {
        enum StackEntry {
            SQLExpr(Box<SQLExpr>),
            Operator(BinaryOperator),
        }

        // Virtual stack machine to convert SQLExpr to Expr
        // This allows visiting the expr tree in a depth-first manner which
        // produces expressions in postfix notations, i.e. `a + b` => `a b +`.
        // See https://github.com/apache/datafusion/issues/1444
        let mut stack = vec![StackEntry::SQLExpr(Box::new(sql))];
        let mut eval_stack = vec![];

        while let Some(entry) = stack.pop() {
            match entry {
                StackEntry::SQLExpr(sql_expr) => {
                    match *sql_expr {
                        SQLExpr::BinaryOp { left, op, right } => {
                            // Note the order that we push the entries to the stack
                            // is important. We want to visit the left node first.
                            stack.push(StackEntry::Operator(op));
                            stack.push(StackEntry::SQLExpr(right));
                            stack.push(StackEntry::SQLExpr(left));
                        }
                        _ => {
                            let expr = self.sql_expr_to_logical_expr_internal(
                                *sql_expr,
                                schema,
                                planner_context,
                            )?;
                            eval_stack.push(expr);
                        }
                    }
                }
                StackEntry::Operator(op) => {
                    let right = eval_stack.pop().unwrap();
                    let left = eval_stack.pop().unwrap();
                    let expr = self.build_logical_expr(op, left, right, schema)?;
                    eval_stack.push(expr);
                }
            }
        }

        assert_eq!(1, eval_stack.len());
        let expr = eval_stack.pop().unwrap();
        Ok(expr)
    }

    fn build_logical_expr(
        &self,