From 35227cdeef9d872890540f212ead9ccc6a9438c4 Mon Sep 17 00:00:00 2001
From: Kevin De Porre <kevin@electric-sql.com>
Date: Wed, 10 Sep 2025 09:49:29 +0200
Subject: [PATCH 1/3] Unit test that reproduces hashing bug with numbers

---
 packages/db-ivm/tests/utils.test.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/db-ivm/tests/utils.test.ts b/packages/db-ivm/tests/utils.test.ts
index a77ddf358..44e3d4680 100644
--- a/packages/db-ivm/tests/utils.test.ts
+++ b/packages/db-ivm/tests/utils.test.ts
@@ -76,6 +76,8 @@ describe(`hash`, () => {
 
       // Same numbers should have same hash
       expect(hash(42)).toBe(result1)
+      expect(hash(2.0)).not.toBe(hash(2.5))
+      expect(hash(3.14159)).toBe(result4)
     })
 
     it(`should hash booleans`, () => {

From b9497434c84976033838d3c74aa1db5da2a8ae89 Mon Sep 17 00:00:00 2001
From: Kevin De Porre <kevin@electric-sql.com>
Date: Wed, 10 Sep 2025 10:08:52 +0200
Subject: [PATCH 2/3] Fix hashing of numbers by hashing all 8 bytes instead of
 only 4 bytes

---
 packages/db-ivm/src/hashing/murmur.ts | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/packages/db-ivm/src/hashing/murmur.ts b/packages/db-ivm/src/hashing/murmur.ts
index bb45f533c..a90b9b72c 100644
--- a/packages/db-ivm/src/hashing/murmur.ts
+++ b/packages/db-ivm/src/hashing/murmur.ts
@@ -20,6 +20,12 @@ export interface Hasher {
   digest: () => number
 }
 
+// Allocate these once, outside the hot path
+const buf = new ArrayBuffer(8)
+// dv and u8 are 2 different views on the same buffer `buf`
+const dv = new DataView(buf)
+const u8 = new Uint8Array(buf)
+
 /**
  * This implementation of Murmur hash uses a random initial seed and random markers.
  * This means that hashes aren't deterministic across app restarts.
@@ -82,10 +88,15 @@ export class MurmurHashStream implements Hasher {
         }
         return
       case `number`:
-        this._writeByte(chunk & 0xff)
-        this._writeByte((chunk >>> 8) & 0xff)
-        this._writeByte((chunk >>> 16) & 0xff)
-        this._writeByte((chunk >>> 24) & 0xff)
+        dv.setFloat64(0, chunk, true) // fixed little-endian
+        this._writeByte(u8[0]!)
+        this._writeByte(u8[1]!)
+        this._writeByte(u8[2]!)
+        this._writeByte(u8[3]!)
+        this._writeByte(u8[4]!)
+        this._writeByte(u8[5]!)
+        this._writeByte(u8[6]!)
+        this._writeByte(u8[7]!)
         return
       case `bigint`: {
         let value = chunk

From 27c83430cec4da8d7adfeb8206ec36dbbac197cc Mon Sep 17 00:00:00 2001
From: Kevin De Porre <kevin@electric-sql.com>
Date: Wed, 10 Sep 2025 10:27:04 +0200
Subject: [PATCH 3/3] Changeset

---
 .changeset/some-lands-matter.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/some-lands-matter.md

diff --git a/.changeset/some-lands-matter.md b/.changeset/some-lands-matter.md
new file mode 100644
index 000000000..47bc08f98
--- /dev/null
+++ b/.changeset/some-lands-matter.md
@@ -0,0 +1,5 @@
+---
+"@tanstack/db-ivm": patch
+---
+
+Fix bug where different numbers would hash to the same value. This caused distinct not to work properly.