Allow setting query transformers in the BaseRAGQA

Related to pathwaycom#67

Add query transformation behavior to `BaseRAGQuestionAnswerer` initialization.

* **`python/pathway/xpacks/llm/question_answering.py`**
  - Add `query_rewrite_method` parameter to `BaseRAGQuestionAnswerer` initialization.
  - Update `answer_query` method to apply the selected query transformation prompt.
  - Use `query_rewrite_method` to select the appropriate query transformation prompt.
  - Add `query_rewrite_method` parameter to `GeometricRAGQuestionAnswerer` initialization.
  - Update `answer_query` method in `GeometricRAGQuestionAnswerer` to apply the selected query transformation prompt.

* **`python/pathway/xpacks/llm/tests/test_rag.py`**
  - Add tests to verify the new functionality of `query_rewrite_method`.
  - Test different values of `query_rewrite_method` parameter.

python/pathway/xpacks/llm/question_answering.py

@@ -307,6 +307,7 @@ class BaseRAGQuestionAnswerer(SummaryQuestionAnswerer):
             A pw.udf function is expected. Defaults to ``pathway.xpacks.llm.prompts.prompt_qa``.
         summarize_template: Template for text summarization. Defaults to ``pathway.xpacks.llm.prompts.prompt_summarize``.
         search_topk: Top k parameter for the retrieval. Adjusts number of chunks in the context.
+        query_rewrite_method: Method for query transformation. Accepts values: 'hyde', 'default', or None. Defaults to None.
 
 
     Example:
@@ -357,6 +358,7 @@ def __init__(
         long_prompt_template: pw.UDF = prompts.prompt_qa,
         summarize_template: pw.UDF = prompts.prompt_summarize,
         search_topk: int = 6,
+        query_rewrite_method: str | None = None,
     ) -> None:
 
         self.llm = llm
@@ -372,6 +374,7 @@ def __init__(
         self.summarize_template = summarize_template
 
         self.search_topk = search_topk
+        self.query_rewrite_method = query_rewrite_method
 
         self.server: None | QASummaryRestServer = None
         self._pending_endpoints: list[tuple] = []
@@ -402,6 +405,15 @@ def answer_query(self, pw_ai_queries: pw.Table) -> pw.Table:
         """Main function for RAG applications that answer questions
         based on available information."""
 
+        if self.query_rewrite_method == "hyde":
+            pw_ai_queries += pw_ai_queries.select(
+                prompt=prompts.prompt_query_rewrite_hyde(pw.this.prompt)
+            )
+        elif self.query_rewrite_method == "default":
+            pw_ai_queries += pw_ai_queries.select(
+                prompt=prompts.prompt_query_rewrite(pw.this.prompt)
+            )
+
         pw_ai_results = pw_ai_queries + self.indexer.retrieve_query(
             pw_ai_queries.select(
                 metadata_filter=pw.this.filters,
@@ -653,6 +665,7 @@ def __init__(
         factor: int = 2,
         max_iterations: int = 4,
         strict_prompt: bool = False,
+        query_rewrite_method: str | None = None,
     ) -> None:
         super().__init__(
             llm,
@@ -661,6 +674,7 @@ def __init__(
             short_prompt_template=short_prompt_template,
             long_prompt_template=long_prompt_template,
             summarize_template=summarize_template,
+            query_rewrite_method=query_rewrite_method,
         )
         self.n_starting_documents = n_starting_documents
         self.factor = factor
@@ -677,6 +691,15 @@ def answer_query(self, pw_ai_queries: pw.Table) -> pw.Table:
         else:
             data_column_name = "text"
 
+        if self.query_rewrite_method == "hyde":
+            pw_ai_queries += pw_ai_queries.select(
+                prompt=prompts.prompt_query_rewrite_hyde(pw.this.prompt)
+            )
+        elif self.query_rewrite_method == "default":
+            pw_ai_queries += pw_ai_queries.select(
+                prompt=prompts.prompt_query_rewrite(pw.this.prompt)
+            )
+
         result = pw_ai_queries.select(
             *pw.this,
             result=answer_with_geometric_rag_strategy_from_index(

python/pathway/xpacks/llm/tests/test_rag.py

@@ -95,3 +95,121 @@ def test_base_rag():
             """
         ),
     )
+
+
+def test_base_rag_with_query_rewrite():
+    schema = pw.schema_from_types(data=bytes, _metadata=dict)
+    input = pw.debug.table_from_rows(
+        schema=schema, rows=[("foo", {}), ("bar", {}), ("baz", {})]
+    )
+
+    vector_server = VectorStoreServer(
+        input,
+        embedder=fake_embeddings_model,
+    )
+
+    rag = BaseRAGQuestionAnswerer(
+        IdentityMockChat(),
+        vector_server,
+        short_prompt_template=_short_template,
+        long_prompt_template=_long_template,
+        summarize_template=_summarize_template,
+        search_topk=2,
+        query_rewrite_method="default",
+    )
+
+    answer_queries = pw.debug.table_from_rows(
+        schema=rag.AnswerQuerySchema,
+        rows=[
+            ("foo", None, "gpt3.5", "short"),
+            ("baz", None, "gpt4", "long"),
+        ],
+    )
+
+    answer_output = rag.answer_query(answer_queries)
+    assert_table_equality(
+        answer_output.select(result=pw.this.result),
+        pw.debug.table_from_markdown(
+            """
+            result
+            gpt3.5,short,foo,foo,bar
+            gpt4,long,baz,baz,bar
+            """
+        ),
+    )
+
+    summarize_query = pw.debug.table_from_rows(
+        schema=rag.SummarizeQuerySchema,
+        rows=[(["foo", "bar"], "gpt2")],
+    )
+
+    summarize_outputs = rag.summarize_query(summarize_query)
+
+    assert_table_equality(
+        summarize_outputs.select(result=pw.this.result),
+        pw.debug.table_from_markdown(
+            """
+            result
+            gpt2,summarize,foo,bar
+            """
+        ),
+    )
+
+
+def test_base_rag_with_hyde_query_rewrite():
+    schema = pw.schema_from_types(data=bytes, _metadata=dict)
+    input = pw.debug.table_from_rows(
+        schema=schema, rows=[("foo", {}), ("bar", {}), ("baz", {})]
+    )
+
+    vector_server = VectorStoreServer(
+        input,
+        embedder=fake_embeddings_model,
+    )
+
+    rag = BaseRAGQuestionAnswerer(
+        IdentityMockChat(),
+        vector_server,
+        short_prompt_template=_short_template,
+        long_prompt_template=_long_template,
+        summarize_template=_summarize_template,
+        search_topk=2,
+        query_rewrite_method="hyde",
+    )
+
+    answer_queries = pw.debug.table_from_rows(
+        schema=rag.AnswerQuerySchema,
+        rows=[
+            ("foo", None, "gpt3.5", "short"),
+            ("baz", None, "gpt4", "long"),
+        ],
+    )
+
+    answer_output = rag.answer_query(answer_queries)
+    assert_table_equality(
+        answer_output.select(result=pw.this.result),
+        pw.debug.table_from_markdown(
+            """
+            result
+            gpt3.5,short,foo,foo,bar
+            gpt4,long,baz,baz,bar
+            """
+        ),
+    )
+
+    summarize_query = pw.debug.table_from_rows(
+        schema=rag.SummarizeQuerySchema,
+        rows=[(["foo", "bar"], "gpt2")],
+    )
+
+    summarize_outputs = rag.summarize_query(summarize_query)
+
+    assert_table_equality(
+        summarize_outputs.select(result=pw.this.result),
+        pw.debug.table_from_markdown(
+            """
+            result
+            gpt2,summarize,foo,bar
+            """
+        ),
+    )