[Bug]: Chat error occurs when "Use Knowledge Graph" is enabled for KG-generated datasets (Reproducible on Infinity only)

[asiroliu]

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RAGFlow workspace code commit ID

9c39ac1

RAGFlow image version

x

Other environment information

infiniflow/infinity:v0.7.0-dev2

Actual behavior

When using a dataset that has already generated a Knowledge Graph (KG) and enabling the "Use Knowledge Graph" option in the Chat configuration, the conversation fails with an error.

Note: This issue is currently only reproducible on the Infinity environment. It works as expected in other tested environments.

Expected behavior

No response

Steps to reproduce

1. Select a dataset with a generated Knowledge Graph.

2. Go to Chat App configuration and toggle on "Use Knowledge Graph".

3. Start a conversation in the Chat App.

Additional information

2026-02-10 11:20:34,814 INFO     21 Q: 为何要强调开张圣听和避免妄自菲薄？, Types: ['BEHAVIOR', 'TONE'], Entities: ['开张圣听', '妄自菲薄', '态度', '自我认知']
2026-02-10 11:20:34,823 ERROR    21 No expression was parsed from ''
Traceback (most recent call last):
  File "/ragflow/api/apps/conversation_app.py", line 224, in stream
    async for ans in async_chat(dia, msg, True, **req):
  File "/ragflow/api/db/services/dialog_service.py", line 443, in async_chat
    ck = await settings.kg_retriever.retrieval(" ".join(questions), tenant_ids, dialog.kb_ids, embd_mdl,
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ragflow/rag/graphrag/search.py", line 169, in retrieval
    ents_from_query = self.get_relevant_ents_by_keywords(ents, filters, idxnms, kb_ids, emb_mdl, ent_sim_threshold)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ragflow/rag/graphrag/search.py", line 114, in get_relevant_ents_by_keywords
    es_res = self.dataStore.search(["content_with_weight", "entity_kwd", "rank_flt"], [], filters, [matchDense],
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ragflow/rag/utils/infinity_conn.py", line 240, in search
    builder = table_instance.output(output)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ragflow/.venv/lib/python3.12/site-packages/infinity/remote_thrift/table.py", line 412, in output
    self.query_builder.output(columns)
  File "/ragflow/.venv/lib/python3.12/site-packages/infinity/remote_thrift/query_builder.py", line 447, in output
    unknown_expr = maybe_parse(column)
                   ^^^^^^^^^^^^^^^^^^^
  File "/ragflow/.venv/lib/python3.12/site-packages/sqlglot/expressions.py", line 8437, in maybe_parse
    return sqlglot.parse_one(sql, read=dialect, into=into, **opts)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ragflow/.venv/lib/python3.12/site-packages/sqlglot/__init__.py", line 144, in parse_one
    raise ParseError(f"No expression was parsed from '{sql}'")
sqlglot.errors.ParseError: No expression was parsed from ''
2026-02-10 11:20:34,827 WARNING  21 /ragflow/api/apps/conversation_app.py:231: RuntimeWarning: coroutine 'Dealer.get_vector' was never awaited
  yield "data:" + json.dumps({"code": 500, "message": str(e), "data": {"answer": "**ERROR**: " + str(e), "reference": []}}, ensure_ascii=False) + "\n\n"

[2026-02-10 11:20:34 +0800] [21] [INFO] 127.0.0.1:43242 POST /v1/conversation/completion 1.1 200 - 10395584

[dosubot]

This is a confirmed compatibility bug between RAGFlow and the Infinity backend, where enabling "Use Knowledge Graph" for KG-generated datasets causes a sqlglot ParseError due to an empty or invalid field name in the query builder's output list. This only happens in the Infinity environment and not with Elasticsearch, so switching to Elasticsearch is a reliable workaround for now source.

The root cause is usually dataset metadata or configuration (like a fields array containing an empty string) that injects blank field names into KG retrieval queries. When Infinity's query builder receives these, it passes an empty string to sqlglot, which fails to parse it source.

To troubleshoot: check your dataset configuration for empty or invalid field names, especially in arrays like fields. If you need to keep using Infinity, try logging the select fields before KG retrieval to spot blanks. Updating to the latest RAGFlow and Infinity versions and cleaning up Infinity data may help, but the bug persists in current builds source.

If you want to help diagnose further, sharing your dataset metadata or logs of the select fields before KG retrieval would be useful. If you have multiple KG-generated datasets, testing whether the bug affects all or only specific ones can clarify if it's a dataset-specific issue.

To reply, just mention @dosu.

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[yuzhichang]

Fixed by #13088