RuntimeError: _Map_base::at When execute MATCH clause with redundant node (hashtag2701)

[vikramsubramanian]

Hi! The following query will cause a strange exception in Kuzu, i.e., RuntimeError: _Map_base::at

MATCH (n1), (n2)<-[]-(n2), (n1)<-[]-(n2) RETURN COUNT (*)

I also have further investigated the case. If I remove the redundant (n1) in the pattern, Kuzu will successfully return the result.

Your help in further confirming and investigating this bug will be highly appreciated.

The graph data for reproduction is as follows: [G.zip](

Best regards, Qiuyang

)

[mayil-ai[bot]]

We're not sure how to solve this one.

but here are some ideas that might help you get started -

Summary: RuntimeError occurs in Kuzu when executing a MATCH clause with a redundant node in the pattern.

Possible Solution

Based on the provided information and code snippets, the issue seems to be related to a Cypher query that is causing a RuntimeError: _Map_base::at exception. This error typically occurs when trying to access a key in a map that does not exist. The problematic query is:

MATCH (n1), (n2)<-[]-(n2), (n1)<-[]-(n2) RETURN COUNT (*)

This query contains a redundancy in the pattern description, which might be causing the error. To resolve the issue, consider the following steps:

• Ensure that the query parser and executor handle node and relationship patterns correctly, especially when the same node is referenced multiple times in a query.
• Check the logic that populates the map or dictionary-like data structure used during query execution to ensure that all necessary keys are present before they are accessed.
• Add validation to the query parser to catch redundant or incorrect patterns before execution.
• Implement proper error handling around map access to provide more informative error messages and prevent runtime errors.

The relevant code snippet that might be directly related to the issue is not provided, but the solution would involve modifying the query execution logic, which is likely part of the CypherQueryExecutor or a similar component in the Kùzu database system.

Code snippets to check

• test/optimizer/optimizer_test.cpp

  The tests in this file are related to the optimizer and logical plan generation, which could be relevant to the issue with the MATCH clause causing a runtime error.

• src/parser/transform/transform_graph_pattern.cpp

  This file is likely involved in the transformation of graph patterns in queries, which could be related to the issue with the redundant node in the MATCH clause.