From 2dd7e5fe08a49dc5a15c9a9a8e3693187a4f6f91 Mon Sep 17 00:00:00 2001
From: He-Pin <hepin1989@gmail.com>
Date: Thu, 13 Aug 2026 19:57:04 +0800
Subject: [PATCH] perf: intern field names and add eq fast path in object field
 lookup

Motivation:
Object field lookup is the hottest path in sjsonnet evaluation. Every
field access (containsKey, containsVisibleKey, valueRaw) compares
String keys char-by-char via .equals, which is wasteful when the same
field names repeat across objects (common in K8s manifests, stdlib).

Modification:
- Parser routes identifier field names (fieldname rule and Expr.Select)
  through internedStrings, sharing String instances across repeated parses
- String-literal field names are interned in the fieldname rule as well,
  with the same >1024 length guard as constructString to avoid memory
  bloat from pathologically large field names
- Val.Obj field lookup hot loops use reference equality (eq) before
  .equals, eliminating char-by-char comparison for interned keys
- 5 lookup sites patched: containsKey (2), containsVisibleKey (1),
  valueRaw (2)

Result:
ParserBenchmark.main: 1.462 -> 1.378 ms/op (-5.7%); MainBenchmark.main
within noise. All 424 tests pass. Zero behavioral change -- eq is
strictly a fast path before the existing .equals fallback (a eq b
implies a.equals(b)).
---
 sjsonnet/src/sjsonnet/Parser.scala | 11 ++++++++---
 sjsonnet/src/sjsonnet/Val.scala    | 11 ++++++-----
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/sjsonnet/src/sjsonnet/Parser.scala b/sjsonnet/src/sjsonnet/Parser.scala
index 8af98afc..bdb339dc 100644
--- a/sjsonnet/src/sjsonnet/Parser.scala
+++ b/sjsonnet/src/sjsonnet/Parser.scala
@@ -679,7 +679,8 @@ class Parser(
       CharIn(".[({")./.!.flatMapX { s =>
         val i = new Position(fileScope, implicitly[P[$]].index - 1)
         (s.charAt(0): @switch) match {
-          case '.' => Pass ~ id.map(x => Expr.Select(i, _: Expr, x))
+          case '.' =>
+            Pass ~ id.map(x => Expr.Select(i, _: Expr, internedStrings.getOrElseUpdate(x, x)))
           case '[' =>
             Pass ~ (expr(currentDepth + 1).? ~ (":" ~ expr(currentDepth + 1).?).rep ~ "]").map {
               case (Some(tree), Seq()) => Expr.Lookup(i, _: Expr, tree)
@@ -1008,8 +1009,12 @@ class Parser(
 
   def fieldname[$: P](currentDepth: Int): P[Expr.FieldName] = {
     P(
-      id.map(Expr.FieldName.Fixed.apply) |
-      string.map(Expr.FieldName.Fixed.apply) |
+      id.map(s => Expr.FieldName.Fixed(internedStrings.getOrElseUpdate(s, s))) |
+      string.map(s =>
+        Expr.FieldName.Fixed(
+          if (s.length > 1024) s else internedStrings.getOrElseUpdate(s, s)
+        )
+      ) |
       "[" ~ expr(currentDepth + 1).map(Expr.FieldName.Dyn.apply) ~ "]"
     )
   }
diff --git a/sjsonnet/src/sjsonnet/Val.scala b/sjsonnet/src/sjsonnet/Val.scala
index b9dc175a..f7fbd1b9 100644
--- a/sjsonnet/src/sjsonnet/Val.scala
+++ b/sjsonnet/src/sjsonnet/Val.scala
@@ -2321,7 +2321,8 @@ object Val {
     }
 
     @inline def containsKey(k: String): Boolean = {
-      if (singleFieldKey != null && `super` == null) singleFieldKey.equals(k)
+      if (singleFieldKey != null && `super` == null)
+        (singleFieldKey eq k) || singleFieldKey.equals(k)
       else if (
         inlineFieldKeys != null && `super` == null && inlineFieldKeys.length <= Obj.InlineScanMax
       ) {
@@ -2329,7 +2330,7 @@ object Val {
         val n = keys.length
         var i = 0
         while (i < n) {
-          if (keys(i).equals(k)) return true
+          if ((keys(i) eq k) || keys(i).equals(k)) return true
           i += 1
         }
         false
@@ -2348,7 +2349,7 @@ object Val {
         val n = keys.length
         var i = 0
         while (i < n) {
-          if (keys(i).equals(k)) return members(i).visibility != Visibility.Hidden
+          if ((keys(i) eq k) || keys(i).equals(k)) return members(i).visibility != Visibility.Hidden
           i += 1
         }
         false
@@ -2495,7 +2496,7 @@ object Val {
         val sfk = singleFieldKey
         if (sfk != null) {
           // Single-field fast path: avoid LinkedHashMap lookup
-          if (sfk.equals(k)) {
+          if ((sfk eq k) || sfk.equals(k)) {
             val m = singleFieldMember
             if (!evaluator.settings.brokenAssertionLogic || !m.deprecatedSkipAsserts) {
               self.triggerAllAsserts(evaluator.settings.brokenAssertionLogic)
@@ -2521,7 +2522,7 @@ object Val {
           val n = keys.length
           var i = 0
           while (i < n) {
-            if (keys(i).equals(k)) {
+            if ((keys(i) eq k) || keys(i).equals(k)) {
               val m = members(i)
               if (!evaluator.settings.brokenAssertionLogic || !m.deprecatedSkipAsserts) {
                 self.triggerAllAsserts(evaluator.settings.brokenAssertionLogic)