Implemented Milvus translator for self-querying (#10162)

- Implemented the MilvusTranslator for self-querying using Milvus vector
store
- Made unit tests to test its functionality
- Documented the Milvus self-querying

libs/langchain/langchain/retrievers/self_query/base.py

@@ -12,6 +12,7 @@ from langchain.retrievers.self_query.chroma import ChromaTranslator
 from langchain.retrievers.self_query.dashvector import DashvectorTranslator
 from langchain.retrievers.self_query.deeplake import DeepLakeTranslator
 from langchain.retrievers.self_query.elasticsearch import ElasticsearchTranslator
+from langchain.retrievers.self_query.milvus import MilvusTranslator
 from langchain.retrievers.self_query.myscale import MyScaleTranslator
 from langchain.retrievers.self_query.pinecone import PineconeTranslator
 from langchain.retrievers.self_query.qdrant import QdrantTranslator
@@ -23,6 +24,7 @@ from langchain.vectorstores import (
     DashVector,
     DeepLake,
     ElasticsearchStore,
+    Milvus,
     MyScale,
     Pinecone,
     Qdrant,
@@ -43,6 +45,7 @@ def _get_builtin_translator(vectorstore: VectorStore) -> Visitor:
         MyScale: MyScaleTranslator,
         DeepLake: DeepLakeTranslator,
         ElasticsearchStore: ElasticsearchTranslator,
+        Milvus: MilvusTranslator,
     }
     if vectorstore_cls not in BUILTIN_TRANSLATORS:
         raise ValueError(

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

@@ -0,0 +1,83 @@
+"""Logic for converting internal query language to a valid Milvus query."""
+from typing import Tuple, Union
+
+from langchain.chains.query_constructor.ir import (
+    Comparator,
+    Comparison,
+    Operation,
+    Operator,
+    StructuredQuery,
+    Visitor,
+)
+
+COMPARATOR_TO_BER = {
+    Comparator.EQ: "==",
+    Comparator.GT: ">",
+    Comparator.GTE: ">=",
+    Comparator.LT: "<",
+    Comparator.LTE: "<=",
+}
+
+UNARY_OPERATORS = [Operator.NOT]
+
+
+def process_value(value: Union[int, float, str]) -> str:
+    # required for comparators involving strings
+    if isinstance(value, str):
+        # 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
+        return str(value)
+
+
+class MilvusTranslator(Visitor):
+    """Translate Milvus internal query language elements to valid filters."""
+
+    """Subset of allowed logical operators."""
+    allowed_operators = [Operator.AND, Operator.NOT, Operator.OR]
+
+    """Subset of allowed logical comparators."""
+    allowed_comparators = [
+        Comparator.EQ,
+        Comparator.GT,
+        Comparator.GTE,
+        Comparator.LT,
+        Comparator.LTE,
+    ]
+
+    def _format_func(self, func: Union[Operator, Comparator]) -> str:
+        self._validate_func(func)
+        value = func.value
+        if isinstance(func, Comparator):
+            value = COMPARATOR_TO_BER[func]
+        return f"{value}"
+
+    def visit_operation(self, operation: Operation) -> str:
+        if operation.operator in UNARY_OPERATORS and len(operation.arguments) == 1:
+            operator = self._format_func(operation.operator)
+            return operator + "(" + operation.arguments[0].accept(self) + ")"
+        elif operation.operator in UNARY_OPERATORS:
+            raise ValueError(
+                f'"{operation.operator.value}" can have only one argument in Milvus'
+            )
+        else:
+            args = [arg.accept(self) for arg in operation.arguments]
+            operator = self._format_func(operation.operator)
+            return "(" + (" " + operator + " ").join(args) + ")"
+
+    def visit_comparison(self, comparison: Comparison) -> str:
+        comparator = self._format_func(comparison.comparator)
+        processed_value = process_value(comparison.value)
+        attribute = comparison.attribute
+
+        return "( " + attribute + " " + comparator + " " + processed_value + " )"
+
+    def visit_structured_query(
+        self, structured_query: StructuredQuery
+    ) -> Tuple[str, dict]:
+        if structured_query.filter is None:
+            kwargs = {}
+        else:
+            kwargs = {"expr": structured_query.filter.accept(self)}
+        return structured_query.query, kwargs

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

@@ -0,0 +1,116 @@
+from typing import Dict, Tuple
+
+from langchain.chains.query_constructor.ir import (
+    Comparator,
+    Comparison,
+    Operation,
+    Operator,
+    StructuredQuery,
+)
+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 )"
+    actual = DEFAULT_TRANSLATOR.visit_comparison(comp)
+
+    assert expected == actual
+
+
+def test_visit_operation() -> None:
+    # Non-Unary operator
+
+    op = Operation(
+        operator=Operator.AND,
+        arguments=[
+            Comparison(comparator=Comparator.LT, attribute="foo", value=2),
+            Comparison(comparator=Comparator.EQ, attribute="bar", value="baz"),
+            Comparison(comparator=Comparator.LT, attribute="abc", value="4"),
+        ],
+    )
+
+    expected = '(( foo < 2 ) and ( bar == "baz" ) ' 'and ( abc < "4" ))'
+    actual = DEFAULT_TRANSLATOR.visit_operation(op)
+
+    assert expected == actual
+
+    # Unary operator: normal execution
+    op = Operation(
+        operator=Operator.NOT,
+        arguments=[
+            Comparison(comparator=Comparator.LT, attribute="foo", value=2),
+        ],
+    )
+
+    expected = "not(( foo < 2 ))"
+    actual = DEFAULT_TRANSLATOR.visit_operation(op)
+
+    assert expected == actual
+
+    # Unary operator: error
+    op = Operation(
+        operator=Operator.NOT,
+        arguments=[
+            Comparison(comparator=Comparator.LT, attribute="foo", value=2),
+            Comparison(comparator=Comparator.EQ, attribute="bar", value="baz"),
+            Comparison(comparator=Comparator.LT, attribute="abc", value="4"),
+        ],
+    )
+
+    try:
+        DEFAULT_TRANSLATOR.visit_operation(op)
+    except ValueError as e:
+        assert str(e) == '"not" can have only one argument in Milvus'
+    else:
+        assert False, "Expected exception not raised"  # No exception -> test failed
+
+
+def test_visit_structured_query() -> None:
+    query = "What is the capital of France?"
+    structured_query = StructuredQuery(
+        query=query,
+        filter=None,
+    )
+    expected: Tuple[str, Dict] = (query, {})
+
+    actual = DEFAULT_TRANSLATOR.visit_structured_query(structured_query)
+    assert expected == actual
+
+    comp = Comparison(comparator=Comparator.LT, attribute="foo", value=454)
+    structured_query = StructuredQuery(
+        query=query,
+        filter=comp,
+    )
+
+    expected = (
+        query,
+        {"expr": "( foo < 454 )"},
+    )
+
+    actual = DEFAULT_TRANSLATOR.visit_structured_query(structured_query)
+    assert expected == actual
+
+    op = Operation(
+        operator=Operator.AND,
+        arguments=[
+            Comparison(comparator=Comparator.LT, attribute="foo", value=2),
+            Comparison(comparator=Comparator.EQ, attribute="bar", value="baz"),
+            Comparison(comparator=Comparator.LT, attribute="abc", value=50),
+        ],
+    )
+
+    structured_query = StructuredQuery(
+        query=query,
+        filter=op,
+    )
+
+    expected = (
+        query,
+        {"expr": "(( foo < 2 ) " 'and ( bar == "baz" ) ' "and ( abc < 50 ))"},
+    )
+
+    actual = DEFAULT_TRANSLATOR.visit_structured_query(structured_query)
+    assert expected == actual