From 5fb4a14234605b4d7ea5ad9f4a99b77c9054a800 Mon Sep 17 00:00:00 2001
From: Ziyang Hu <hu.ziyang@cantab.net>
Date: Thu, 19 May 2022 22:42:51 +0800
Subject: [PATCH] avoid unnecessary evaluation

---
 src/data/eval.rs | 75 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 48 insertions(+), 27 deletions(-)

diff --git a/src/data/eval.rs b/src/data/eval.rs
index 35209a65..815b1ad0 100644
--- a/src/data/eval.rs
+++ b/src/data/eval.rs
@@ -116,44 +116,65 @@ impl<'a> Expr<'a> {
                 //     expr => expr.partial_eval(ctx)?,
                 // };
                 // match expr {expr
-                match arg.partial_eval(ctx)? {
-                    Expr::Const(Value::Null) => Expr::Const(Value::Null),
-                    Expr::Const(Value::Dict(mut d)) => {
-                        Expr::Const(d.remove(&f as &str).unwrap_or(Value::Null))
+                match *arg {
+                    Expr::Dict(mut d) => {
+                        // This skips evaluation of other keys
+                        d.remove(&f as &str)
+                            .unwrap_or(Expr::Const(Value::Null))
+                            .partial_eval(ctx)?
+                    }
+                    arg => {
+                        match arg.partial_eval(ctx)? {
+                            Expr::Const(Value::Null) => Expr::Const(Value::Null),
+                            Expr::Const(Value::Dict(mut d)) => {
+                                Expr::Const(d.remove(&f as &str).unwrap_or(Value::Null))
+                            }
+                            v @ (Expr::IdxAcc(_, _)
+                            | Expr::FieldAcc(_, _)
+                            | Expr::TableCol(_, _)
+                            | Expr::Apply(_, _)
+                            | Expr::ApplyAgg(_, _, _)) => Expr::FieldAcc(f, v.into()),
+                            Expr::Dict(mut d) => d.remove(&f as &str).unwrap_or(Expr::Const(Value::Null)),
+                            v => return Err(EvalError::FieldAccess(f, Value::from(v).to_static())),
+                        }
                     }
-                    v @ (Expr::IdxAcc(_, _)
-                    | Expr::FieldAcc(_, _)
-                    | Expr::TableCol(_, _)
-                    | Expr::Apply(_, _)
-                    | Expr::ApplyAgg(_, _, _)) => Expr::FieldAcc(f, v.into()),
-                    Expr::Dict(mut d) => d.remove(&f as &str).unwrap_or(Expr::Const(Value::Null)),
-                    v => return Err(EvalError::FieldAccess(f, Value::from(v).to_static())),
                 }
             }
             Expr::IdxAcc(i, arg) => {
-                let arg = arg.partial_eval(ctx)?;
-                match arg {
-                    Expr::Const(Value::Null) => Expr::Const(Value::Null),
-                    Expr::Const(Value::List(mut l)) => {
+                match *arg {
+                    // This skips evaluation of other keys
+                    Expr::List(mut l) => {
                         if i >= l.len() {
                             Expr::Const(Value::Null)
                         } else {
-                            Expr::Const(l.swap_remove(i))
+                            l.swap_remove(i).partial_eval(ctx)?
                         }
                     }
-                    Expr::List(mut l) => {
-                        if i >= l.len() {
-                            Expr::Const(Value::Null)
-                        } else {
-                            l.swap_remove(i)
+                    arg => {
+                        match arg.partial_eval(ctx)? {
+                            Expr::Const(Value::Null) => Expr::Const(Value::Null),
+                            Expr::Const(Value::List(mut l)) => {
+                                if i >= l.len() {
+                                    Expr::Const(Value::Null)
+                                } else {
+                                    Expr::Const(l.swap_remove(i))
+                                }
+                            }
+                            Expr::List(mut l) => {
+                                if i >= l.len() {
+                                    Expr::Const(Value::Null)
+                                } else {
+                                    l.swap_remove(i)
+                                }
+                            }
+                            v @ (Expr::IdxAcc(_, _)
+                            | Expr::FieldAcc(_, _)
+                            | Expr::TableCol(_, _)
+                            | Expr::Apply(_, _)
+                            | Expr::ApplyAgg(_, _, _)) => Expr::IdxAcc(i, v.into()),
+                            v => return Err(EvalError::IndexAccess(i, Value::from(v).to_static())),
                         }
                     }
-                    v @ (Expr::IdxAcc(_, _)
-                    | Expr::FieldAcc(_, _)
-                    | Expr::TableCol(_, _)
-                    | Expr::Apply(_, _)
-                    | Expr::ApplyAgg(_, _, _)) => Expr::IdxAcc(i, v.into()),
-                    v => return Err(EvalError::IndexAccess(i, Value::from(v).to_static())),
                 }
             }
             Expr::Apply(op, args) => {