Improved readme and tests

Author: ankane

README.md

@@ -182,13 +182,17 @@ Also supports `sum`
 Add an approximate index
 
 ```python
-index = Index('my_index', Item.embedding,
+index = Index(
+    'my_index',
+    Item.embedding,
     postgresql_using='hnsw',
     postgresql_with={'m': 16, 'ef_construction': 64},
     postgresql_ops={'embedding': 'vector_l2_ops'}
 )
 # or
-index = Index('my_index', Item.embedding,
+index = Index(
+    'my_index',
+    Item.embedding,
     postgresql_using='ivfflat',
     postgresql_with={'lists': 100},
     postgresql_ops={'embedding': 'vector_l2_ops'}
@@ -255,6 +259,32 @@ session.exec(select(func.avg(Item.embedding))).first()
 
 Also supports `sum`
 
+Add an approximate index
+
+```python
+from sqlalchemy import Index
+
+index = Index(
+    'my_index',
+    Item.embedding,
+    postgresql_using='hnsw',
+    postgresql_with={'m': 16, 'ef_construction': 64},
+    postgresql_ops={'embedding': 'vector_l2_ops'}
+)
+# or
+index = Index(
+    'my_index',
+    Item.embedding,
+    postgresql_using='ivfflat',
+    postgresql_with={'lists': 100},
+    postgresql_ops={'embedding': 'vector_l2_ops'}
+)
+
+index.create(engine)
+```
+
+Use `vector_ip_ops` for inner product and `vector_cosine_ops` for cosine distance
+
 ## Psycopg 3
 
 Enable the extension

tests/test_sqlalchemy.py

@@ -25,6 +25,15 @@ class Item(Base):
 Base.metadata.drop_all(engine)
 Base.metadata.create_all(engine)
 
+index = Index(
+    'orm_index',
+    Item.embedding,
+    postgresql_using='hnsw',
+    postgresql_with={'m': 16, 'ef_construction': 64},
+    postgresql_ops={'embedding': 'vector_l2_ops'}
+)
+index.create(engine)
+
 
 def create_items():
     vectors = [

tests/test_sqlmodel.py

@@ -1,7 +1,7 @@
 import numpy as np
 from pgvector.sqlalchemy import Vector
 import pytest
-from sqlalchemy import Column
+from sqlalchemy import Column, Index
 from sqlalchemy.exc import StatementError
 from sqlalchemy.sql import func
 from sqlmodel import Field, Session, SQLModel, create_engine, delete, select, text
@@ -22,6 +22,15 @@ class Item(SQLModel, table=True):
 SQLModel.metadata.drop_all(engine)
 SQLModel.metadata.create_all(engine)
 
+index = Index(
+    'sqlmodel_index',
+    Item.embedding,
+    postgresql_using='hnsw',
+    postgresql_with={'m': 16, 'ef_construction': 64},
+    postgresql_ops={'embedding': 'vector_l2_ops'}
+)
+index.create(engine)
+
 
 def create_items():
     vectors = [