Can you query multiple dbs in one (fabric) cypher statement?

[mike]

Hi,

We are evaluating fabric but before testing I wanted to find out if there are any limitations on cypher queries (including GDS)

I understand this is possible:
Query db#1 and use output as input for a query to db#2

And also this;
Query db#1 and combine output with output from a query to db#2 (using UNION)

But is this possible?
Construct a query which includes labels/properties from both db#1 and db#2

e.g.

WITH ["db#1", "db#2"] AS dbs
UNWIND fabric.graphIds() AS graphId
CALL {
  USE fabric.graph(graphId)
  OPTIONAL MATCH (db1:Label {db1prop: ""})-[COMMON_REL]-(db2:Label { db2prop: ""})
  .....

If this could work I assume it would depend on having the node and relationship labels identical in both.

I read this but am still not clear

Mark Needham – 3 Feb 20

Neo4j: Cross database querying with Neo4j Fabric · Mark Needham

Learn how to write cross database queries against an Australian Open Graph using Neo4j Fabric.

[michael_hunger]

Yes if both have the same labels and rel-types you can send the same query to all shards.

But you currently cannot have relationships that span shards, so you need to have proxy nodes of that other shard that carry at least the id, to continue matching from.

[mike]

thanks for clarifying @michael.hunger