From 13397911e207d6f7f7ef134a0bb19cee2cec0f3c Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Mon, 9 Sep 2024 20:49:13 -0700
Subject: [PATCH] Added SparseVector class

---
 CHANGELOG.md            |  2 +-
 lib/pgvector.dart       |  2 ++
 lib/sparsevec.dart      | 28 ++++++++++++++++++++++++++++
 test/postgres_test.dart |  9 ++++++---
 4 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100644 lib/sparsevec.dart

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e2328df..571e279 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 ## 0.1.1 (unreleased)
 
-- Added `Vector` and `HalfVector` classes
+- Added `Vector`, `HalfVector`, and `SparseVector` classes
 
 ## 0.1.0 (2023-10-17)
 
diff --git a/lib/pgvector.dart b/lib/pgvector.dart
index 9b28eea..13c319d 100644
--- a/lib/pgvector.dart
+++ b/lib/pgvector.dart
@@ -2,9 +2,11 @@ import 'dart:convert';
 import 'dart:typed_data';
 
 import 'halfvec.dart';
+import 'sparsevec.dart';
 import 'vector.dart';
 
 export 'halfvec.dart' show HalfVector;
+export 'sparsevec.dart' show SparseVector;
 export 'vector.dart' show Vector;
 
 class Pgvector {
diff --git a/lib/sparsevec.dart b/lib/sparsevec.dart
new file mode 100644
index 0000000..2d9de22
--- /dev/null
+++ b/lib/sparsevec.dart
@@ -0,0 +1,28 @@
+class SparseVector {
+  final int dimensions;
+  final List<int> indices;
+  final List<double> values;
+
+  SparseVector._(this.dimensions, this.indices, this.values);
+
+  factory SparseVector(List<double> value) {
+    var dimensions = value.length;
+    var indices = <int>[];
+    var values = <double>[];
+    for (var i = 0; i < value.length; i++) {
+      if (value[i] != 0) {
+        indices.add(i);
+        values.add(value[i]);
+      }
+    }
+    return SparseVector._(dimensions, indices, values);
+  }
+
+  @override
+  String toString() {
+    var elements = [
+      for (var i = 0; i < indices.length; i++) "${indices[i] + 1}:${values[i]}"
+    ].join(",");
+    return "{${elements}}/${this.dimensions}";
+  }
+}
diff --git a/test/postgres_test.dart b/test/postgres_test.dart
index 34407ef..8e5c294 100644
--- a/test/postgres_test.dart
+++ b/test/postgres_test.dart
@@ -17,18 +17,21 @@ void main() {
     await connection.execute("DROP TABLE IF EXISTS items");
 
     await connection.execute(
-        "CREATE TABLE items (id bigserial PRIMARY KEY, embedding vector(3), half_embedding halfvec(3))");
+        "CREATE TABLE items (id bigserial PRIMARY KEY, embedding vector(3), half_embedding halfvec(3), sparse_embedding sparsevec(3))");
 
     await connection.execute(
         Sql.named(
-            "INSERT INTO items (embedding, half_embedding) VALUES (@a, @d), (@b, @e), (@c, @f)"),
+            "INSERT INTO items (embedding, half_embedding, sparse_embedding) VALUES (@a, @d, @g), (@b, @e, @h), (@c, @f, @i)"),
         parameters: {
           "a": Vector([1, 1, 1]).toString(),
           "b": Vector([2, 2, 2]).toString(),
           "c": Vector([1, 1, 2]).toString(),
           "d": HalfVector([1, 1, 1]).toString(),
           "e": HalfVector([2, 2, 2]).toString(),
-          "f": HalfVector([1, 1, 2]).toString()
+          "f": HalfVector([1, 1, 2]).toString(),
+          "g": SparseVector([1, 1, 1]).toString(),
+          "h": SparseVector([2, 2, 2]).toString(),
+          "i": SparseVector([1, 1, 2]).toString()
         });
 
     List<List<dynamic>> results = await connection.execute(