ArcadeDB 26.8.1: `REMOVE` label after `OPTIONAL MATCH` raises an edge-list `RecordNotFoundException`

[YGY-001]

Environment

• ArcadeDB Docker image: arcadedata/arcadedb:26.8.1

Steps to reproduce

Run the following Cypher on an empty, disposable Test database.

MATCH (n) DETACH DELETE n;

CREATE (n0 {k9:true})-[:rt7]->(n1:l1 {tag:'middle'})-[:X]->(n2 {tag:'end'});
MATCH (n1 {tag:'middle'}) CREATE (n1)-[:c]->(:Extra);

UNWIND ['x'] AS alias0
OPTIONAL MATCH (n2)<-[]-(n1)<-[:rt7]-(n0), p0=(n2)
WHERE true
WITH *
WHERE n1 IS NOT NULL AND n0 IS NOT NULL
REMOVE n0.k9, n1:l1
RETURN count(*) AS row_count;

Expected result

The query completes and returns row_count = 1. Removing n1:l1 should update the label set without corrupting or losing the vertex's edge records.

Actual result

The query fails deterministically on a fresh database with a server-side exception equivalent to:

Cannot load OUT edge list chunk (#5:0) for vertex #4:0
com.arcadedb.exception.RecordNotFoundException: Record #5:0 not found
  at com.arcadedb.graph.GraphEngine.getEdges
  at com.arcadedb.query.sql.executor.RemoveStep.removeLabels

[lvca]

Fixed in #6326 (merged).

One note on the expected value, since it differs from the report: the query matches 2 rows, not 1. The fixture gives the middle node two outgoing edges - [:X]->(n2 {tag:'end'}) from the first CREATE, and the [:c]->(:Extra) added by the second - and (n2)<-[]-(n1) matches both. The regression test asserts 2 for that reason. The exception you reported was real and is what the fix addresses: a label removal has to rewrite the vertex (ArcadeDB reads a record's type from its bucket, and a label set is a type), and the second row was still holding the record the first row deleted.