Querying all databases

To query all known shards, we will have to use two other functions:

• fabric.graphIds(), which returns all the known databases. You can test its result with the following command:

RETURN fabric.graphIds()

• fabric.graph(graphId) returns the name of the database with a given ID, directly usable in a Use statement.

This will essentially allow us to perform a loop over all our shards:

UNWIND fabric.graphIds() AS graphId
CALL {
  USE fabric.graph(graphId)
    WITH graphId
    MATCH (order:Order)<--(:User)-->(country:Country)
    RETURN "gr" + graphId as db,
           country.name as countryName,
           count(*) AS nbOrders
 } RETURN db, countryName, sum(nbOrders)

Here is the result of the preceding query:

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