Fix sparse vector Map serialization with out-of-order indices

src/sparse-vector.js

@@ -108,14 +108,22 @@ export class SparseVector {
     this.dimensions = Number(dimensions);
 
     const entries = map instanceof Map ? map.entries() : Object.entries(map);
+    /** @type {Array<[number, number]>} */
+    const elements = [];
     for (const [i, v] of entries) {
       const f = Number(v);
       if (f != 0) {
-        this.indices.push(Number(i));
-        this.values.push(f);
+        elements.push([Number(i), f]);
       }
     }
 
+    // PostgreSQL requires sparsevec indices in ascending order.
+    elements.sort((a, b) => a[0] - b[0]);
+    for (const [i, v] of elements) {
+      this.indices.push(i);
+      this.values.push(v);
+    }
+
     // TODO uncomment in 0.4.0
     // this.#validate();
   }

tests/pg.test.js

@@ -29,6 +29,11 @@ test('pg example', async () => {
   assert.deepEqual(rows[0].binary_embedding, '000');
   assert.deepEqual(rows[0].sparse_embedding.toArray(), [1, 1, 1]);
 
+  // Map insertion order is not necessarily the order required by sparsevec.
+  const sparse = new SparseVector(new Map([[2, 3], [0, 1]]), 3);
+  const result = await client.query('INSERT INTO pg_items (sparse_embedding) VALUES ($1) RETURNING sparse_embedding', [sparse]);
+  assert.deepEqual(result.rows[0].sparse_embedding.toArray(), [1, 0, 3]);
+
   await client.query('CREATE INDEX ON pg_items USING hnsw (embedding vector_l2_ops)');
 
   await client.end();

tests/sparse-vector.test.js

@@ -34,8 +34,19 @@ test('fromMap', () => {
   map.set(3, 0);
   const vec = new SparseVector(map, 6);
   assert.equal(vec.dimensions, 6);
-  assert.deepEqual(vec.indices, [2, 4, 0]);
-  assert.deepEqual(vec.values, [2, 3, 1]);
+  assert.deepEqual(vec.indices, [0, 2, 4]);
+  assert.deepEqual(vec.values, [1, 2, 3]);
+  assert.equal(vec.toPostgres(), '{1:1,3:2,5:3}/6');
+  assert.deepEqual(vec.toArray(), [1, 0, 2, 0, 3, 0]);
+});
+
+test('fromMapUnsortedNegativeValues', () => {
+  const map = new Map([[5, -4.5], [1, 0], [3, -2], [0, 1.25]]);
+  const vec = new SparseVector(map, 7);
+  assert.deepEqual(vec.indices, [0, 3, 5]);
+  assert.deepEqual(vec.values, [1.25, -2, -4.5]);
+  assert.equal(vec.toPostgres(), '{1:1.25,4:-2,6:-4.5}/7');
+  assert.deepEqual([...map], [[5, -4.5], [1, 0], [3, -2], [0, 1.25]]);
 });
 
 test('fromMapObject', () => {