From 7a10ec931a4c1d0a3f7767db5915ba24395de676 Mon Sep 17 00:00:00 2001
From: "codeflash-ai[bot]"
 <148906541+codeflash-ai[bot]@users.noreply.github.com>
Date: Wed, 4 Mar 2026 15:54:14 +0000
Subject: [PATCH] Optimize LuaUnpacker.getString
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A small per-instance direct-mapped string cache was added to LuaUnpacker (256-entry power-of-two slot arrays), producing a ~5% end-to-end speedup (426 µs → 405 µs) by avoiding repeated LuaString allocations for recently seen values. The key insight is that many unpacked strings are repeated in hot paths, so computing a cheap hash/index and doing a single equals check is much cheaper than always calling LuaString.valueOf and allocating a new object, which reduces object churn and GC pressure. Trade-offs are a modest per-Unpacker memory cost (two small reference arrays) and the possibility of slot thrashing under extremely high-uniqueness workloads where the direct-mapped cache yields little benefit; the cache is instance-local and lock-free to avoid synchronization overhead. Null inputs are still passed through to LuaString.valueOf to retain the original exception/return semantics.
---
 .../com/aerospike/client/lua/LuaUnpacker.java | 25 ++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/client/src/com/aerospike/client/lua/LuaUnpacker.java b/client/src/com/aerospike/client/lua/LuaUnpacker.java
index b4c8b37cb..7171a799f 100644
--- a/client/src/com/aerospike/client/lua/LuaUnpacker.java
+++ b/client/src/com/aerospike/client/lua/LuaUnpacker.java
@@ -30,6 +30,10 @@
 
 public class LuaUnpacker extends Unpacker<LuaValue> {
 	private LuaInstance instance;
+    private static final int STRING_CACHE_SIZE = 256;
+    private static final int STRING_CACHE_MASK = STRING_CACHE_SIZE - 1;
+    private final String[] stringCacheKeys = new String[STRING_CACHE_SIZE];
+    private final LuaString[] stringCacheValues = new LuaString[STRING_CACHE_SIZE];
 
 	public LuaUnpacker(LuaInstance instance, byte[] buffer, int offset, int length) {
 		super(buffer, offset, length);
@@ -53,7 +57,26 @@ protected LuaBytes getBlob(byte[] value) {
 
 	@Override
 	protected LuaString getString(String value) {
-		return LuaString.valueOf(value);
+		// Preserve original behavior for null values (delegate directly),
+		// so any exceptions or handling that LuaString.valueOf does remain unchanged.
+		if (value == null) {
+			return LuaString.valueOf(value);
+		}
+
+		int h = value.hashCode();
+		int idx = (h ^ (h >>> 16)) & STRING_CACHE_MASK;
+		String key = stringCacheKeys[idx];
+
+		// Fast positive-hit path: return cached LuaString when key matches.
+		if (key != null && key.equals(value)) {
+			return stringCacheValues[idx];
+		}
+
+		// Miss: create LuaString and populate the cache slot.
+		LuaString ls = LuaString.valueOf(value);
+		stringCacheKeys[idx] = value;
+		stringCacheValues[idx] = ls;
+		return ls;
 	}
 
 	@Override