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KùzuDB Integration Fixes - Summary

Issues Identified and Resolved

1. Polymorphic MERGE Not Supported

Problem: KùzuDB doesn't support creating relationships where endpoints can be multiple node types (e.g., MATCH (n) WHERE (n:Function OR n:Class)).

Error: Binder exception: Create rel bound by multiple node labels is not supported.

Solution: Modified graph_builder.py to use separate, specific queries for each type combination:

  • Function → Function
  • Function → Class
  • Class → Function
  • Class → Class
  • File → Function
  • File → Class

Each query uses OPTIONAL MATCH with WHERE IS NOT NULL checks and returns a count to determine if the relationship was created.

2. ORDER BY Scope Issues with DISTINCT

Problem: KùzuDB requires ORDER BY to use result aliases when DISTINCT is present, not direct property access.

Error: Binder exception: Variable <name> is not in scope.

Solution: Updated all ORDER BY clauses in code_finder.py to use result aliases:

  • Changed ORDER BY caller.is_dependency → ORDER BY caller_is_dependency
  • Changed ORDER BY called.name → ORDER BY called_function

3. Schema Property Mismatches

Problem: KùzuDB schema was missing properties that the indexer tries to set (end_line, decorators).

Solution: Updated database_kuzu.py node table schemas to include:

  • end_line INT64 for all code element types
  • decorators STRING[] for Function and Class types

4. Variable-Length Path Syntax Limitations ✅ RESOLVED

Problem: KùzuDB doesn't allow binding the end node in variable-length path patterns.

Error: Parser exception: Invalid input <(end> when using (start)-[:CALLS*]->(end)

Solution: Use anonymous end nodes () and extract the target using path functions:

MATCH p = (start:Function)-[:CALLS*1..5]->()
WITH p, nodes(p) as path_nodes
WITH list_extract(path_nodes, size(path_nodes)) as end_node
WHERE end_node.name = $target_name

Key KùzuDB Path Functions:

  • nodes(path) - Returns array of nodes in path
  • relationships(path) - Returns array of relationships
  • length(path) - Returns path length
  • size(list) - Returns list size
  • list_extract(list, index) - Extracts element at index (1-based)

Files Modified

  1. src/codegraphcontext/tools/graph_builder.py

    • Replaced polymorphic MERGE queries with type-specific fallback queries
    • Added KùzuDB-specific workarounds for relationship creation

  2. src/codegraphcontext/tools/code_finder.py

    • Updated ORDER BY clauses to use result aliases
    • Fixed scope issues in query methods
    • Updated variable-length path queries (find_all_callers, find_all_callees, find_function_call_chain)

  3. src/codegraphcontext/core/database_kuzu.py

    • Added missing schema properties (end_line, decorators)
    • Added name property for backend identification

Testing Results

✅ Working:

  • Repository indexing
  • Function/Class/Variable extraction
  • Basic queries (find, stats, list)
  • CALLS relationship creation
  • CONTAINS relationship creation
  • Variable-length path queries (analyze callers, analyze callees, analyze chain)

⚠️ Known Limitations:

  • Cannot bind end node in variable-length patterns (workaround implemented)
  • Union label syntax (MATCH (n:Function|Class)) not supported
  • FOREACH clause not supported
  • COALESCE with node variables in MERGE not supported
  • Polymorphic MERGE not supported (workaround implemented)

Recommendations

  1. Disable debug logging: Remove or comment out the DEBUG_KUZU print statements in database_kuzu.py for production use.

  2. Performance consideration: Variable-length path queries with anonymous end nodes may be slower than Neo4j's direct binding. Monitor performance on large codebases.

  3. Document limitations: Update user documentation to note KùzuDB-specific syntax differences.

  4. Future work: Consider adding a query optimizer layer that automatically rewrites queries based on the active backend.

KùzuDB Version Tested

  • KùzuDB 0.11.3