community[patch]: Make some functions work with Milvus (#10695)

**Description**
Make some functions work with Milvus:
1. get_ids: Get primary keys by field in the metadata
2. delete: Delete one or more entities by ids
3. upsert: Update/Insert one or more entities

**Issue**
None
**Dependencies**
None
**Tag maintainer:**
@hwchase17 
**Twitter handle:**
None

---------

Co-authored-by: HoaNQ9 <hoanq.1811@gmail.com>
Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/vectorstores/milvus.py

@@ -989,3 +989,64 @@ class Milvus(VectorStore):
             page_content=data.pop(self._text_field),
             metadata=data.pop(self._metadata_field) if self._metadata_field else data,
         )
+
+    def get_pks(self, expr: str, **kwargs: Any) -> List[int] | None:
+        """Get primary keys with expression
+
+        Args:
+            expr: Expression - E.g: "id in [1, 2]", or "title LIKE 'Abc%'"
+
+        Returns:
+            List[int]: List of IDs (Primary Keys)
+        """
+
+        from pymilvus import MilvusException
+
+        if self.col is None:
+            logger.debug("No existing collection to get pk.")
+            return None
+
+        try:
+            query_result = self.col.query(
+                expr=expr, output_fields=[self._primary_field]
+            )
+        except MilvusException as exc:
+            logger.error("Failed to get ids: %s error: %s", self.collection_name, exc)
+            raise exc
+        pks = [item.get(self._primary_field) for item in query_result]
+        return pks
+
+    def upsert(
+        self,
+        ids: Optional[List[str]] = None,
+        documents: List[Document] | None = None,
+        **kwargs: Any,
+    ) -> List[str] | None:
+        """Update/Insert documents to the vectorstore.
+
+        Args:
+            ids: IDs to update - Let's call get_pks to get ids with expression \n
+            documents (List[Document]): Documents to add to the vectorstore.
+
+        Returns:
+            List[str]: IDs of the added texts.
+        """
+
+        from pymilvus import MilvusException
+
+        if documents is None or len(documents) == 0:
+            logger.debug("No documents to upsert.")
+            return None
+
+        if ids is not None and len(ids):
+            try:
+                self.delete(ids=ids)
+            except MilvusException:
+                pass
+        try:
+            return self.add_documents(documents=documents)
+        except MilvusException as exc:
+            logger.error(
+                "Failed to upsert entities: %s error: %s", self.collection_name, exc
+            )
+            raise exc