langchain[patch]: support more comparators in Milvus self-querying retriever (#16076)

- **Description:** Support IN and LIKE comparators in Milvus
self-querying retriever, based on [Boolean Expression
Rules](https://milvus.io/docs/boolean.md)
  - **Issue:** No
  - **Dependencies:** No
  - **Twitter handle:** No

Signed-off-by: ChengZi <chen.zhang@zilliz.com>

libs/langchain/langchain/retrievers/self_query/milvus.py

@@ -16,28 +16,36 @@ COMPARATOR_TO_BER = {
     Comparator.GTE: ">=",
     Comparator.LT: "<",
     Comparator.LTE: "<=",
+    Comparator.IN: "in",
+    Comparator.LIKE: "like",
 }
 
 UNARY_OPERATORS = [Operator.NOT]
 
 
-def process_value(value: Union[int, float, str]) -> str:
+def process_value(value: Union[int, float, str], comparator: Comparator) -> str:
     """Convert a value to a string and add double quotes if it is a string.
 
     It required for comparators involving strings.
 
     Args:
         value: The value to convert.
+        comparator: The comparator.
 
     Returns:
         The converted value as a string.
     """
     #
     if isinstance(value, str):
-        # If the value is already a string, add double quotes
-        return f'"{value}"'
+        if comparator is Comparator.LIKE:
+            # If the comparator is LIKE, add a percent sign after it for prefix matching
+            # and add double quotes
+            return f'"{value}%"'
+        else:
+            # If the value is already a string, add double quotes
+            return f'"{value}"'
     else:
-        # If the valueis not a string, convert it to a string without double quotes
+        # If the value is not a string, convert it to a string without double quotes
         return str(value)
 
 
@@ -54,6 +62,8 @@ class MilvusTranslator(Visitor):
         Comparator.GTE,
         Comparator.LT,
         Comparator.LTE,
+        Comparator.IN,
+        Comparator.LIKE,
     ]
 
     def _format_func(self, func: Union[Operator, Comparator]) -> str:
@@ -78,7 +88,7 @@ class MilvusTranslator(Visitor):
 
     def visit_comparison(self, comparison: Comparison) -> str:
         comparator = self._format_func(comparison.comparator)
-        processed_value = process_value(comparison.value)
+        processed_value = process_value(comparison.value, comparison.comparator)
         attribute = comparison.attribute
 
         return "( " + attribute + " " + comparator + " " + processed_value + " )"

libs/langchain/tests/unit_tests/retrievers/self_query/test_milvus.py

@@ -1,4 +1,6 @@
-from typing import Dict, Tuple
+from typing import Any, Dict, Tuple
+
+import pytest
 
 from langchain.chains.query_constructor.ir import (
     Comparator,
@@ -12,11 +14,22 @@ from langchain.retrievers.self_query.milvus import MilvusTranslator
 DEFAULT_TRANSLATOR = MilvusTranslator()
 
 
-def test_visit_comparison() -> None:
-    comp = Comparison(comparator=Comparator.LT, attribute="foo", value=4)
-    expected = "( foo < 4 )"
+@pytest.mark.parametrize(
+    "triplet",
+    [
+        (Comparator.EQ, 2, "( foo == 2 )"),
+        (Comparator.GT, 2, "( foo > 2 )"),
+        (Comparator.GTE, 2, "( foo >= 2 )"),
+        (Comparator.LT, 2, "( foo < 2 )"),
+        (Comparator.LTE, 2, "( foo <= 2 )"),
+        (Comparator.IN, ["bar", "abc"], "( foo in ['bar', 'abc'] )"),
+        (Comparator.LIKE, "bar", '( foo like "bar%" )'),
+    ],
+)
+def test_visit_comparison(triplet: Tuple[Comparator, Any, str]) -> None:
+    comparator, value, expected = triplet
+    comp = Comparison(comparator=comparator, attribute="foo", value=value)
     actual = DEFAULT_TRANSLATOR.visit_comparison(comp)
-
     assert expected == actual