Bolt: integer property values silently coerced to strings after `CREATE INDEX`, and index-backed property lookups return empty

[mpreusse]

Found while pointing the test suite of graphio (a Python OGM / bulk loader originally written for Neo4j) at ArcadeDB. graphio creates indexes on merge-key properties and wipes the graph between tests — exactly the pattern that triggers this. Some tests fail silently against ArcadeDB, all tracing back to the issue below.

Summary

After a CREATE INDEX on a node property, the same DELETE + re-CREATE cycle that worked moments earlier starts:

• storing integer property values as strings (the literal 1 is read back as '1')
• returning empty results for property-equality lookups (MATCH (n:Label {prop: 1}) and WHERE n.prop = 1 both return []), even though a label-only MATCH finds the node

The bug is not triggered by DELETE + re-CREATE alone — only after at least one CREATE INDEX has been run in the same database session/lifetime. The control sequence (no index) round-trips integer values correctly.

This affects any client that combines secondary indexes with cyclical data churn — for example, test suites that wipe the graph between tests (MATCH (n) DETACH DELETE n) and rely on property-equality MERGE/MATCH against indexed merge keys.

Reproduction

Self-contained Python script using the official Neo4j driver (Bolt). The only difference between Part 1 and Part 2 is a single CREATE INDEX line.

1. Start a fresh ArcadeDB container

The --rm + no-volume combo ensures a clean state. Studio UI at http://localhost:2480 (login root / testtest).

docker rm -f arcadedb-repro 2>/dev/null; \
docker run -d --rm --name arcadedb-repro \
    -p 7687:7687 \
    -p 2480:2480 \
    -e JAVA_OPTS="-Darcadedb.server.rootPassword=testtest \
        -Darcadedb.server.plugins=Bolt:com.arcadedb.bolt.BoltProtocolPlugin \
        -Darcadedb.server.defaultDatabases=somedb[] \
        -Darcadedb.bolt.defaultDatabase=somedb" \
    arcadedata/arcadedb:latest && sleep 5

2. Install the driver and run the script

pip install neo4j
python arcadedb_repro.py

3. The script

from neo4j import GraphDatabase

driver = GraphDatabase.driver('bolt://localhost:7687', auth=('root', 'testtest'))


def run(cypher):
    with driver.session() as session:
        return [dict(r) for r in session.run(cypher)]


# =============================================================================
# PART 1 — Without CREATE INDEX (works correctly)
# =============================================================================

print('=== PART 1: WITHOUT CREATE INDEX ===\n')

run('MATCH (n) DETACH DELETE n')
run("CREATE (a:Person {uuid: 1})")
run('MATCH (n) DETACH DELETE n')
run("CREATE (a:Person {uuid: 1})")

print('  MATCH (n:Person) RETURN n.uuid                  ->',
      run('MATCH (n:Person) RETURN n.uuid AS u'))
print('  MATCH (n:Person {uuid: 1}) RETURN n.uuid        ->',
      run('MATCH (n:Person {uuid: 1}) RETURN n.uuid AS u'))
print('  MATCH (n:Person) WHERE n.uuid = 1 RETURN n.uuid ->',
      run('MATCH (n:Person) WHERE n.uuid = 1 RETURN n.uuid AS u'))


# =============================================================================
# PART 2 — Same sequence + a single CREATE INDEX (broken)
# =============================================================================

print('\n=== PART 2: SAME — but with one CREATE INDEX added ===\n')

run('MATCH (n) DETACH DELETE n')
run("CREATE (a:Person {uuid: 1})")
run('CREATE INDEX IF NOT EXISTS FOR (n:Person) ON (n.uuid)')   # <-- only change
run('MATCH (n) DETACH DELETE n')
run("CREATE (a:Person {uuid: 1})")

print('  MATCH (n:Person) RETURN n.uuid                  ->',
      run('MATCH (n:Person) RETURN n.uuid AS u'))
print('  MATCH (n:Person {uuid: 1}) RETURN n.uuid        ->',
      run('MATCH (n:Person {uuid: 1}) RETURN n.uuid AS u'))
print('  MATCH (n:Person) WHERE n.uuid = 1 RETURN n.uuid ->',
      run('MATCH (n:Person) WHERE n.uuid = 1 RETURN n.uuid AS u'))

driver.close()

Expected vs. actual output

=== PART 1: WITHOUT CREATE INDEX ===

  MATCH (n:Person) RETURN n.uuid                  -> [{'u': 1}]
  MATCH (n:Person {uuid: 1}) RETURN n.uuid        -> [{'u': 1}]
  MATCH (n:Person) WHERE n.uuid = 1 RETURN n.uuid -> [{'u': 1}]

=== PART 2: SAME — but with one CREATE INDEX added ===

  MATCH (n:Person) RETURN n.uuid                  -> [{'u': '1'}]
  MATCH (n:Person {uuid: 1}) RETURN n.uuid        -> []
  MATCH (n:Person) WHERE n.uuid = 1 RETURN n.uuid -> []

Expected on every line: [{'u': 1}] (integer).

Actual in Part 2:

Query	Returned	What's wrong
MATCH (n:Person) RETURN n.uuid	[{'u': '1'}]	Integer literal 1 stored as the string '1'.
MATCH (n:Person {uuid: 1}) RETURN ...	[]	Lookup fails — the node exists (count > 0), but the index doesn't find it.
MATCH (n:Person) WHERE n.uuid = 1 RETURN ...	[]	Same — index-backed WHERE filter returns empty.

Environment

ArcadeDB	26.6.1-SNAPSHOT (image arcadedata/arcadedb:latest)
Bolt plugin	Neo4j-Bolt v4.0, TLS disabled
Client	neo4j Python driver 5.x
Python	3.12
Host	macOS arm64, Docker Desktop

Related observations

These may be the same underlying issue, or two separate things — worth mentioning together because they compound in real applications:

1. Bolt write counters are always empty. result.consume().counters returns {} even for queries that clearly created/deleted records. This makes the bug above invisible to client code: rs.create() returns successfully, the script believes it wrote the data, and only a follow-up MATCH reveals that no data is reachable by property filter.

2. Inconsistent error vs. silent failure. In some repeated runs, the same UNWIND $rels AS rel MATCH (a:X), (b:Y) WHERE ... CREATE ... pattern raises Neo.DatabaseError.General.UnknownError; in others it returns success with no rows changed. Possibly related to the same index-state corruption.

Impact in the wild

I hit this while trying to point graphio — a Python OGM / bulk loader originally written for Neo4j — at ArcadeDB. graphio creates indexes on merge-key properties (standard practice), and its test suite calls MATCH (n) DETACH DELETE n between tests. With those two ingredients, some of graphio's tests fail silently against ArcadeDB — rs.create() reports success, but MATCH ... RETURN count(r) returns 0. The test failure pattern is what led me to the reproducer above.

Happy to test patches or provide additional debug output.

[lvca]

@mpreusse reproduced and fixed on main branch.

[lvca]

If you want to test this fix, please check out: https://docs.arcadedb.com/arcadedb/appendix/latest-build#latest-build-local

[mpreusse]

Fantastic, thanks. I'll try!