From 7f2bc90bc55e8ed7bfc752e6e104c46d4e69b0b6 Mon Sep 17 00:00:00 2001
From: Gengliang Wang <gengliang@apache.org>
Date: Sat, 30 May 2026 11:14:41 +0000
Subject: [PATCH] [SPARK-57174][SQL] Simplify Chr codegen by extracting a
 static Java helper

### What changes were proposed in this pull request?

Add `ExpressionImplUtils.chr(long longVal)` and route `Chr`'s eval and codegen
paths through it. `Chr.doGenCode` previously emitted a ~7-line inline if/else
chain (negative -> empty string, `(v & 0xFF) == 0` -> NUL, otherwise the
Latin-1 character); it now emits a single `ExpressionImplUtils.chr(...)` call,
and the eval path calls the same helper.

This is a plain (non-ANSI, non-try/catch) type-independent block, in line with
the broadened goal of SPARK-56908 to move fixed generated-Java logic into static
Java helpers.

### Why are the changes needed?

Part of SPARK-56908 (umbrella). Collapsing the inline if/else chain to one call
shrinks the generated Java for every stage that uses `chr`.

### Does this PR introduce _any_ user-facing change?

No. The compiled behavior is identical; only the emitted Java source text changes.

### How was this patch tested?

```
build/sbt "catalyst/testOnly *StringExpressionsSuite"
```

59/59 pass, including `string for ascii` which covers `Chr` over negative, zero,
wrap-around (256), high-bit (149) and null inputs (exercised both with and
without whole-stage codegen).

### Was this patch authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Opus 4.8)

Co-authored-by: Isaac
---
 .../expressions/ExpressionImplUtils.java      | 17 ++++++++++++++
 .../expressions/stringExpressions.scala       | 23 +++----------------
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/ExpressionImplUtils.java b/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/ExpressionImplUtils.java
index a5228edc33c83..ded5c96525e22 100644
--- a/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/ExpressionImplUtils.java
+++ b/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/ExpressionImplUtils.java
@@ -342,4 +342,21 @@ public static UTF8String quote(UTF8String str) {
     String sp = str.toString().replaceAll(qtChar, qtCharRep);
     return UTF8String.fromString(qtChar + sp + qtChar);
   }
+
+  /**
+   * Returns the single-character string for the {@code chr} expression: the
+   * ASCII/Latin-1 character for {@code longVal & 0xFF}. A negative argument
+   * yields the empty string. Shared by the eval and codegen paths so the
+   * generated Java is a single call rather than an inline if/else chain.
+   */
+  public static UTF8String chr(long longVal) {
+    if (longVal < 0) {
+      return UTF8String.EMPTY_UTF8;
+    } else if ((longVal & 0xFF) == 0) {
+      return UTF8String.fromString(String.valueOf(Character.MIN_VALUE));
+    } else {
+      char c = (char) (longVal & 0xFF);
+      return UTF8String.fromString(String.valueOf(c));
+    }
+  }
 }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
index 5b5a63812dcab..5c6e457421bf6 100755
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
@@ -2822,31 +2822,14 @@ case class Chr(child: Expression)
   override def inputTypes: Seq[DataType] = Seq(LongType)
 
   protected override def nullSafeEval(lon: Any): Any = {
-    val longVal = lon.asInstanceOf[Long]
-    if (longVal < 0) {
-      UTF8String.EMPTY_UTF8
-    } else if ((longVal & 0xFF) == 0) {
-      UTF8String.fromString(Character.MIN_VALUE.toString)
-    } else {
-      UTF8String.fromString((longVal & 0xFF).toChar.toString)
-    }
+    ExpressionImplUtils.chr(lon.asInstanceOf[Long])
   }
 
   override def contextIndependentFoldable: Boolean = child.contextIndependentFoldable
 
   override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
-    nullSafeCodeGen(ctx, ev, lon => {
-      s"""
-        if ($lon < 0) {
-          ${ev.value} = UTF8String.EMPTY_UTF8;
-        } else if (($lon & 0xFF) == 0) {
-          ${ev.value} = UTF8String.fromString(String.valueOf(Character.MIN_VALUE));
-        } else {
-          char c = (char)($lon & 0xFF);
-          ${ev.value} = UTF8String.fromString(String.valueOf(c));
-        }
-      """
-    })
+    val utils = classOf[ExpressionImplUtils].getName
+    nullSafeCodeGen(ctx, ev, lon => s"${ev.value} = $utils.chr($lon);")
   }
 
   override protected def withNewChildInternal(newChild: Expression): Chr = copy(child = newChild)