diff --git a/src/milvus_haystack/document_store.py b/src/milvus_haystack/document_store.py
index 66854be..20ae196 100644
--- a/src/milvus_haystack/document_store.py
+++ b/src/milvus_haystack/document_store.py
@@ -10,8 +10,21 @@
 from haystack.document_stores.types import DuplicatePolicy
 from haystack.errors import FilterError
 from haystack.utils import Secret, deserialize_secrets_inplace
-from pymilvus import AnnSearchRequest, MilvusException, RRFRanker
+from pymilvus import (
+    AnnSearchRequest,
+    Collection,
+    CollectionSchema,
+    DataType,
+    FieldSchema,
+    MilvusClient,
+    MilvusException,
+    RRFRanker,
+    connections,
+    utility,
+)
 from pymilvus.client.abstract import BaseRanker
+from pymilvus.client.types import LoadState
+from pymilvus.orm.types import infer_dtype_bydata
 
 from milvus_haystack.filters import parse_filters
 
@@ -122,17 +135,9 @@ def __init__(
         :param replica_number: Number of replicas. Defaults to 1.
         :param timeout: Timeout in seconds. Defaults to None.
         """
-        try:
-            from pymilvus import Collection, utility
-        except ImportError as err:
-            err_msg = "Could not import pymilvus python package. Please install it with `pip install pymilvus`."
-            raise ValueError(err_msg) from err
-
         # Default search params when one is not provided.
         self.default_search_params = {
-            "GPU_IVF_FLAT": {"metric_type": "L2", "params": {"nprobe": 10}},
-            "GPU_IVF_PQ": {"metric_type": "L2", "params": {"nprobe": 10}},
-            "GPU_CAGRA": {"metric_type": "L2", "params": {"itopk_size": 128}},
+            "FLAT": {"metric_type": "L2", "params": {}},
             "IVF_FLAT": {"metric_type": "L2", "params": {"nprobe": 10}},
             "IVF_SQ8": {"metric_type": "L2", "params": {"nprobe": 10}},
             "IVF_PQ": {"metric_type": "L2", "params": {"nprobe": 10}},
@@ -142,7 +147,16 @@ def __init__(
             "RHNSW_PQ": {"metric_type": "L2", "params": {"ef": 10}},
             "IVF_HNSW": {"metric_type": "L2", "params": {"nprobe": 10, "ef": 10}},
             "ANNOY": {"metric_type": "L2", "params": {"search_k": 10}},
+            "SCANN": {"metric_type": "L2", "params": {"search_k": 10}},
             "AUTOINDEX": {"metric_type": "L2", "params": {}},
+            "GPU_CAGRA": {"metric_type": "L2", "params": {"itopk_size": 128}},
+            "GPU_IVF_FLAT": {"metric_type": "L2", "params": {"nprobe": 10}},
+            "GPU_IVF_PQ": {"metric_type": "L2", "params": {"nprobe": 10}},
+            "SPARSE_INVERTED_INDEX": {
+                "metric_type": "IP",
+                "params": {"drop_ratio_build": 0.2},
+            },
+            "SPARSE_WAND": {"metric_type": "IP", "params": {"drop_ratio_build": 0.2}},
         }
 
         self.collection_name = collection_name
@@ -169,6 +183,9 @@ def __init__(
         # Create the connection to the server
         if connection_args is None:
             self.connection_args = DEFAULT_MILVUS_CONNECTION
+        self._milvus_client = MilvusClient(
+            **self.connection_args,
+        )
         self.alias = self._create_connection_alias(self.connection_args)  # type: ignore[arg-type]
         self.col: Optional[Collection] = None
 
@@ -193,6 +210,11 @@ def __init__(
         )
         self._dummy_value = 999.0
 
+    @property
+    def client(self) -> MilvusClient:
+        """Get client."""
+        return self._milvus_client
+
     def count_documents(self) -> int:
         """
         Returns how many documents are present in the document store.
@@ -311,8 +333,6 @@ def write_documents(self, documents: List[Document], policy: DuplicatePolicy = D
         :return: Number of documents written.
         """
 
-        from pymilvus import Collection, MilvusException
-
         documents_cp = [MilvusDocumentStore._discard_invalid_meta(doc) for doc in deepcopy(documents)]
         if len(documents_cp) > 0 and not isinstance(documents_cp[0], Document):
             err_msg = "param 'documents' must contain a list of objects of type Document"
@@ -484,8 +504,6 @@ def from_dict(cls, data: Dict[str, Any]) -> "MilvusDocumentStore":
 
     def _create_connection_alias(self, connection_args: dict) -> str:
         """Create the connection to the Milvus server."""
-        from pymilvus import MilvusException, connections
-
         connection_args_cp = copy.deepcopy(connection_args)
         # Grab the connection arguments that are used for checking existing connection
         host: str = connection_args_cp.get("host", None)
@@ -568,15 +586,6 @@ def _init(
         )
 
     def _create_collection(self, embeddings: list, metas: Optional[List[Dict]] = None) -> None:
-        from pymilvus import (
-            Collection,
-            CollectionSchema,
-            DataType,
-            FieldSchema,
-            MilvusException,
-        )
-        from pymilvus.orm.types import infer_dtype_bydata
-
         # Determine embedding dim
         dim = len(embeddings[0])
         fields = []
@@ -630,8 +639,6 @@ def _create_collection(self, embeddings: list, metas: Optional[List[Dict]] = Non
 
     def _extract_fields(self) -> None:
         """Grab the existing fields from the Collection"""
-        from pymilvus import Collection
-
         if isinstance(self.col, Collection):
             schema = self.col.schema
             for x in schema.fields:
@@ -639,8 +646,6 @@ def _extract_fields(self) -> None:
 
     def _create_index(self) -> None:
         """Create an index on the collection"""
-        from pymilvus import Collection, MilvusException
-
         if isinstance(self.col, Collection) and self._get_index() is None:
             try:
                 # If no index params, use a default HNSW based one
@@ -694,8 +699,6 @@ def _create_index(self) -> None:
 
     def _create_search_params(self) -> None:
         """Generate search params based on the current index type"""
-        from pymilvus import Collection
-
         if isinstance(self.col, Collection) and self.search_params is None:
             index = self._get_index()
             if index is not None:
@@ -706,8 +709,6 @@ def _create_search_params(self) -> None:
 
     def _get_index(self) -> Optional[Dict[str, Any]]:
         """Return the vector index information if it exists"""
-        from pymilvus import Collection
-
         if isinstance(self.col, Collection):
             for x in self.col.indexes:
                 if x.field_name == self._vector_field:
@@ -721,9 +722,6 @@ def _load(
         timeout: Optional[float] = None,
     ) -> None:
         """Load the collection if available."""
-        from pymilvus import Collection, utility
-        from pymilvus.client.types import LoadState
-
         if (
             isinstance(self.col, Collection)
             and self._get_index() is not None
@@ -901,6 +899,8 @@ def _map_ip_to_similarity(ip_score: float) -> float:
             """
             return (ip_score + 1) / 2.0
 
+        if not self.index_params:
+            return lambda x: x
         metric_type = self.index_params.get("metric_type", None)
         if metric_type == "L2":
             return _map_l2_to_similarity
@@ -942,9 +942,6 @@ def _discard_invalid_meta(document: Document):
         """
         Remove metadata fields with unsupported types from the document.
         """
-        from pymilvus import DataType
-        from pymilvus.orm.types import infer_dtype_bydata
-
         if not isinstance(document, Document):
             msg = f"Invalid document type: {type(document)}"
             raise ValueError(msg)
diff --git a/tests/test_document_store.py b/tests/test_document_store.py
index 9c07963..4609a5c 100644
--- a/tests/test_document_store.py
+++ b/tests/test_document_store.py
@@ -79,6 +79,6 @@ def test_to_and_from_dict(self, document_store: MilvusDocumentStore):
         assert document_store_dict == expected_dict
         reconstructed_document_store = MilvusDocumentStore.from_dict(document_store_dict)
         for field in vars(reconstructed_document_store):
-            if field.startswith("__") or field == "alias":
+            if field.startswith("__") or field in ["alias", "_milvus_client"]:
                 continue
             assert getattr(reconstructed_document_store, field) == getattr(document_store, field)
diff --git a/tests/test_embedding_retriever.py b/tests/test_embedding_retriever.py
index 0dbd9e9..bf40272 100644
--- a/tests/test_embedding_retriever.py
+++ b/tests/test_embedding_retriever.py
@@ -148,7 +148,7 @@ def test_from_dict(self, document_store: MilvusDocumentStore):
                 continue
             elif field == "document_store":
                 for doc_store_field in vars(document_store):
-                    if doc_store_field.startswith("__") or doc_store_field == "alias":
+                    if doc_store_field.startswith("__") or doc_store_field in ["alias", "_milvus_client"]:
                         continue
                     assert getattr(reconstructed_retriever.document_store, doc_store_field) == getattr(
                         document_store, doc_store_field
@@ -286,7 +286,7 @@ def test_from_dict(self, document_store: MilvusDocumentStore):
                 continue
             elif field == "document_store":
                 for doc_store_field in vars(document_store):
-                    if doc_store_field.startswith("__") or doc_store_field == "alias":
+                    if doc_store_field.startswith("__") or doc_store_field in ["alias", "_milvus_client"]:
                         continue
                     assert getattr(reconstructed_retriever.document_store, doc_store_field) == getattr(
                         document_store, doc_store_field
@@ -433,7 +433,7 @@ def test_from_dict(self, document_store: MilvusDocumentStore):
                 continue
             elif field == "document_store":
                 for doc_store_field in vars(document_store):
-                    if doc_store_field.startswith("__") or doc_store_field == "alias":
+                    if doc_store_field.startswith("__") or doc_store_field in ["alias", "_milvus_client"]:
                         continue
                     assert getattr(reconstructed_retriever.document_store, doc_store_field) == getattr(
                         document_store, doc_store_field