apoc.meta.data() reports wrong property type information

[neo-technology-build-agent]

Issue by moxious Thursday Oct 17, 2019 at 18:50 GMT Originally opened as https://github.com/neo4j-contrib/neo4j-apoc-procedures/issues/1319

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Replication that worked for me:

create (:A { x: 1 }), (:A { x: 'Foo' });
create (:B { x: 'Foo' }), (:B { x: 'Foo' }), (:B { x: 1 });
CALL apoc.meta.data();

This setup is intentionally to confuse APOC. For both labels A and B, the property X is typed both string and long.

The APOC call:

This procedure uses a sampling configuration as specified by the config parameters, which is a MetaConfig object. The sampling appears respected, but the property type information stored in the MetaResult class is "last type in wins".

I would say this behavior is incorrect. There are two possible correct behaviors:

1. Return an array of different types the property could have, as observed in the sample ["Long", "String"]
2. Perform some type-coercion, and always report "String" as a single property type, because it is the widest of all observed types.