[rjb32]

Reject a MERGE whose key property is null on any row.

[rjb32]

Note

AI-generated summary.

Summary

The analyzer rejects a MERGE key that is null by type. A key that is null on some rows only reached the executor, which wrote the entity without that property. The check now runs in the executor, on every row's key values, before any row is matched or written.

 NLMergeExecutor::run
   extractProperties(rowCount)
   for each node
     throwIfBoundNodeIsNull
+    throwIfKeyIsNull(node._properties)
+  for each hop
+    throwIfKeyIsNull(hop._properties)
   for each row
     matchRow(row)        // match, or writeRow

The error text is the analyzer's: MERGE cannot match on property 'name', which is null.

Evidence

• Before: 5 of the 6 new MergeRejectionTest cases failed: each query succeeded instead of being rejected.
  After: test_query_ir_merge_rejection passes all 11 cases.

rejectsANodeKeyThatIsNullByType           MERGE (t:Tag {name: 'k', flag: 1 < 'a'})                        (analyzer, passed before)
rejectsANodeKeyThatIsNullOnOneRow         UNWIND [null, 'a'] AS v MERGE (t:Tag {name: v}) RETURN t.name
rejectsANodeKeyThatIsNullOnTheLastRow     UNWIND ['a', 'b', null] AS v MERGE (t:Tag {name: v})
rejectsANodeKeyACaseMakesNullOnOneRow     MATCH (p:Person) MERGE (t:Tag {name: CASE WHEN p.name = 'Remy' THEN null ELSE p.name END})
rejectsANodeKeyReadFromAMissingProperty   MATCH (p:Person) MERGE (t:Tag {name: 'x', age: p.age})
rejectsAnEdgeKeyThatIsNullOnOneRow        MATCH (a:Person {name: 'Remy'}), (b:Person {name: 'Adam'}) UNWIND [1, null] AS w MERGE (a)-[:PROBE {weight: w}]->(b)

The 57 test_query_ir_(merge|set|write|create|subquery) targets and V3QueryTestSuite pass.

Merge Danger

Door: two-way

Blast Radius: MERGE

A MERGE with a null key on any row now fails where it used to succeed. Neo4j fails the same queries.