diff --git a/common/metadata_utils.py b/common/metadata_utils.py
index 772606714..cbe6dfe7c 100644
--- a/common/metadata_utils.py
+++ b/common/metadata_utils.py
@@ -19,9 +19,6 @@ from typing import Any, Callable, Dict
 
 import json_repair
 
-from rag.prompts.generator import gen_meta_filter
-
-
 def convert_conditions(metadata_condition):
     if metadata_condition is None:
         metadata_condition = {}
@@ -62,9 +59,9 @@ def meta_filter(metas: dict, filters: list[dict], logic: str = "and"):
             matched = False
             try:
                 if operator == "contains":
-                    matched = input in value if not isinstance(input, list) else all(i in value for i in input)
+                    matched = str(input).find(value) >= 0 if not isinstance(input, list) else any(str(i).find(value) >= 0 for i in input)
                 elif operator == "not contains":
-                    matched = input not in value if not isinstance(input, list) else all(i not in value for i in input)
+                    matched = str(input).find(value) == -1 if not isinstance(input, list) else all(str(i).find(value) == -1 for i in input)
                 elif operator == "in":
                     matched = input in value if not isinstance(input, list) else all(i in value for i in input)
                 elif operator == "not in":
@@ -133,6 +130,8 @@ async def apply_meta_data_filter(
         list of doc_ids, ["-999"] when manual filters yield no result, or None
         when auto/semi_auto filters return empty.
     """
+    from rag.prompts.generator import gen_meta_filter # move from the top of the file to avoid circular import
+
     doc_ids = list(base_doc_ids) if base_doc_ids else []
 
     if not meta_data_filter:
diff --git a/test/unit_test/common/test_metadata_filter_operators.py b/test/unit_test/common/test_metadata_filter_operators.py
new file mode 100644
index 000000000..90ee64e31
--- /dev/null
+++ b/test/unit_test/common/test_metadata_filter_operators.py
@@ -0,0 +1,113 @@
+from common.metadata_utils import meta_filter
+
+
+def test_contains():
+    # returns chunk where the metadata contains the value
+    metas = {"version": {"hello earth": ["doc1"], "hello mars": ["doc2"]}}
+    filters = [{"key": "version", "op": "contains", "value": "earth"}]
+
+    assert meta_filter(metas, filters) == ["doc1"]
+
+
+def test_not_contains():
+    # returns chunk where the metadata does not contain the value
+    metas = {"version": {"hello earth": ["doc1"], "hello mars": ["doc2"]}}
+    filters = [{"key": "version", "op": "not contains", "value": "earth"}]
+
+    assert meta_filter(metas, filters) == ["doc2"]
+
+
+def test_in_operator():
+    # returns chunk where the metadata is in the value
+    metas = {"status": {"active": ["doc1"], "pending": ["doc2"], "done": ["doc3"]}}
+    filters = [{"key": "status", "op": "in", "value": "active,pending"}]
+
+    assert set(meta_filter(metas, filters)) == {"doc1", "doc2"}
+
+
+def test_not_in_operator():
+    # returns chunk where the metadata is not in the value
+    metas = {"status": {"active": ["doc1"], "pending": ["doc2"], "done": ["doc3"]}}
+    filters = [{"key": "status", "op": "not in", "value": "active,pending"}]
+
+    assert meta_filter(metas, filters) == ["doc3"]
+
+
+def test_start_with():
+    # returns chunk where the metadata starts with the value
+    metas = {"name": {"prefix_value": ["doc1"], "other": ["doc2"]}}
+    filters = [{"key": "name", "op": "start with", "value": "pre"}]
+
+    assert meta_filter(metas, filters) == ["doc1"]
+
+
+def test_end_with():
+    # returns chunk where the metadata ends with the value
+    metas = {"file": {"report.pdf": ["doc1"], "image.png": ["doc2"]}}
+    filters = [{"key": "file", "op": "end with", "value": ".pdf"}]
+
+    assert meta_filter(metas, filters) == ["doc1"]
+
+
+def test_empty():
+    # returns chunk where the metadata is empty
+    metas = {"notes": {"": ["doc1"], "non-empty": ["doc2"]}}
+    filters = [{"key": "notes", "op": "empty", "value": ""}]
+
+    assert meta_filter(metas, filters) == ["doc1"]
+
+
+def test_not_empty():
+    # returns chunk where the metadata is not empty
+    metas = {"notes": {"": ["doc1"], "non-empty": ["doc2"]}}
+    filters = [{"key": "notes", "op": "not empty", "value": ""}]
+
+    assert meta_filter(metas, filters) == ["doc2"]
+
+
+def test_equal():
+    # returns chunk where the metadata is equal to the value
+    metas = {"score": {"5": ["doc1"], "6": ["doc2"]}}
+    filters = [{"key": "score", "op": "=", "value": "5"}]
+
+    assert meta_filter(metas, filters) == ["doc1"]
+
+
+def test_not_equal():
+    # returns chunk where the metadata is not equal to the value
+    metas = {"score": {"5": ["doc1"], "6": ["doc2"]}}
+    filters = [{"key": "score", "op": "≠", "value": "5"}]
+
+    assert meta_filter(metas, filters) == ["doc2"]
+
+
+def test_greater_than():
+    # returns chunk where the metadata is greater than the value
+    metas = {"score": {"10": ["doc1"], "2": ["doc2"]}}
+    filters = [{"key": "score", "op": ">", "value": "5"}]
+
+    assert meta_filter(metas, filters) == ["doc1"]
+
+
+def test_less_than():
+    # returns chunk where the metadata is less than the value
+    metas = {"score": {"10": ["doc1"], "2": ["doc2"]}}
+    filters = [{"key": "score", "op": "<", "value": "5"}]
+
+    assert meta_filter(metas, filters) == ["doc2"]
+
+
+def test_greater_than_or_equal():
+    # returns chunk where the metadata is greater than or equal to the value
+    metas = {"score": {"5": ["doc1"], "6": ["doc2"], "4": ["doc3"]}}
+    filters = [{"key": "score", "op": "≥", "value": "5"}]
+
+    assert set(meta_filter(metas, filters)) == {"doc1", "doc2"}
+
+
+def test_less_than_or_equal():
+    # returns chunk where the metadata is less than or equal to the value
+    metas = {"score": {"5": ["doc1"], "6": ["doc2"], "4": ["doc3"]}}
+    filters = [{"key": "score", "op": "≤", "value": "5"}]
+
+    assert set(meta_filter(metas, filters)) == {"doc1", "doc3"}