Fix relation direction creation with merge and create, fixes #3326

[ExtReMLapin]

fixes #3326

All cypher tests passes, didn't write any test for them, feel free to add them

[gemini-code-assist]

Summary of Changes

Hello @ExtReMLapin, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request fixes a bug where relationship direction was not correctly handled during MERGE and CREATE operations in Cypher queries. The fix ensures that when an incoming relationship (IN direction) is specified, the correct vertices are assigned as the source and target of the edge, resolving issue #3326.

Highlights

• Bug Fix: Addresses issue Cypher : relations are always created left to right even if arrow is going from right to left #3326 related to incorrect directionality when creating relationships using MERGE and CREATE statements in Cypher queries.
• Direction Handling: The code now correctly handles the IN direction for relationships in both CreateStep and MergeStep, ensuring that the fromVertex and toVertex are assigned appropriately based on the relationship direction.
• Code Modification: The changes involve adding a check for relPattern.getDirection() and swapping fromVertex and toVertex accordingly when the direction is IN.

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Changelog

• engine/src/main/java/com/arcadedb/query/opencypher/executor/steps/CreateStep.java
  • Imported Direction class from com.arcadedb.query.opencypher.ast.
  • Modified createPath method to handle IN direction for relationships, swapping fromVertex and toVertex accordingly.
• engine/src/main/java/com/arcadedb/query/opencypher/executor/steps/MergeStep.java
  • Imported Direction class from com.arcadedb.query.opencypher.ast.
  • Modified mergePath method to handle IN direction for relationships, swapping fromVertex and toVertex accordingly.

Activity

• The pull request addresses issue Cypher : relations are always created left to right even if arrow is going from right to left #3326.
• All Cypher tests passed.
• The author suggests adding more tests specifically for these changes.

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[gemini-code-assist]

Code Review

This pull request correctly addresses issue #3326 by handling relationship direction in CREATE and MERGE operations. The logic for swapping from and to vertices for incoming relationships is correct.

However, I have two suggestions for improvement:

• Testing: As you noted in the description, tests are missing. It is important to add regression tests to OpenCypherCreateTest.java and OpenCypherMergeTest.java to verify the fix for incoming relationship directions and prevent future regressions. A test case could involve creating/merging a pattern like (a)<-[:REL]-(b) and asserting that the edge is created from b to a.
• Code Duplication: The logic to determine the from and to vertices is duplicated across CreateStep.java and MergeStep.java. I've left a comment with a suggestion to refactor this.

Addressing these points will make the contribution even stronger.

[gemini-code-assist]

This logic for determining fromVertex and toVertex is duplicated in MergeStep.java (lines 282-291). To adhere to the DRY (Don't Repeat Yourself) principle and improve maintainability, please consider extracting this logic into a common helper method that can be used by both CreateStep and MergeStep.

[codecov]

Codecov Report

❌ Patch coverage is 40.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.94%. Comparing base (d6cbc10) to head (3bbc685).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...db/query/opencypher/executor/steps/CreateStep.java	40.00%	2 Missing and 1 partial ⚠️
...edb/query/opencypher/executor/steps/MergeStep.java	40.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3353      +/-   ##
==========================================
- Coverage   56.97%   56.94%   -0.03%     
==========================================
  Files        1368     1368              
  Lines      100624   100630       +6     
  Branches    20490    20492       +2     
==========================================
- Hits        57326    57303      -23     
- Misses      34205    34223      +18     
- Partials     9093     9104      +11     

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[mergify]

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