fix caching (#658)

Author: hwchase17

langchain/cache.py

@@ -60,7 +60,7 @@ def __init__(self, engine: Engine, cache_schema: Any = FullLLMCache):
         """Initialize by creating all tables."""
         self.engine = engine
         self.cache_schema = cache_schema
-        Base.metadata.create_all(self.engine)
+        self.cache_schema.metadata.create_all(self.engine)
 
     def lookup(self, prompt: str, llm_string: str) -> Optional[RETURN_VAL_TYPE]:
         """Look up based on prompt and llm_string."""

tests/unit_tests/llms/test_base.py

@@ -1,6 +1,9 @@
 """Test base LLM functionality."""
+from sqlalchemy import Column, Integer, Sequence, String, create_engine
+from sqlalchemy.ext.declarative import declarative_base
+
 import langchain
-from langchain.cache import InMemoryCache
+from langchain.cache import InMemoryCache, SQLAlchemyCache
 from langchain.schema import Generation, LLMResult
 from tests.unit_tests.llms.fake_llm import FakeLLM
 
@@ -28,3 +31,41 @@ def test_caching() -> None:
         llm_output=None,
     )
     assert output == expected_output
+
+
+def test_custom_caching() -> None:
+    """Test custom_caching behavior."""
+    Base = declarative_base()
+
+    class FulltextLLMCache(Base):  # type: ignore
+        """Postgres table for fulltext-indexed LLM Cache."""
+
+        __tablename__ = "llm_cache_fulltext"
+        id = Column(Integer, Sequence("cache_id"), primary_key=True)
+        prompt = Column(String, nullable=False)
+        llm = Column(String, nullable=False)
+        idx = Column(Integer)
+        response = Column(String)
+
+    engine = create_engine("sqlite://")
+    langchain.llm_cache = SQLAlchemyCache(engine, FulltextLLMCache)
+    llm = FakeLLM()
+    params = llm._llm_dict()
+    params["stop"] = None
+    llm_string = str(sorted([(k, v) for k, v in params.items()]))
+    langchain.llm_cache.update("foo", llm_string, [Generation(text="fizz")])
+    output = llm.generate(["foo", "bar", "foo"])
+    expected_cache_output = [Generation(text="foo")]
+    cache_output = langchain.llm_cache.lookup("bar", llm_string)
+    assert cache_output == expected_cache_output
+    langchain.llm_cache = None
+    expected_generations = [
+        [Generation(text="fizz")],
+        [Generation(text="foo")],
+        [Generation(text="fizz")],
+    ]
+    expected_output = LLMResult(
+        expected_generations,
+        llm_output=None,
+    )
+    assert output == expected_output